LOS ANGELES, Calif. - After a spate of vandalism and violence, Los Angeles police vowed Tuesday to crack down with quick action and arrests if further disturbances arise from street protests over the acquittal of George Zimmerman in the killing of a black Florida teenager.

Chief Charlie Beck and Mayor Eric Garcetti, who took office barely two weeks ago, said peaceful protests are welcome but violence won't be tolerated. Beck vowed that anyone committing violence will be arrested.

"Your actions ... will reduce the power of the message of this community and that is wrong, that is a shameful act," he said.

Los Angeles and Oakland have been flashpoints for violent reactions to Saturday's acquittal of Zimmerman in the death of Trayvon Martin.

In the Crenshaw District of Los Angeles, 14 people were arrested Monday night after about 150 people split from a peaceful demonstration at a park, running through the streets, jumping on cars, trying to break store windows and punching bystanders. A Wal-Mart store was vandalized.

A reporter and photographer for Los Angeles TV stations KCBS and KCAL also were assaulted and transported to a hospital with minor injuries. A police officer was punched in the chest on Sunday and a 24-year-old man, Brandon Bell, was charged Tuesday with battery and resisting arrest.

Deputy Chief Bob Green, who heads the LAPD's South Bureau, said officers were pelted with rocks as they stood by monitoring the protest. He blamed the incidents on "knuckleheads" from outside the area who are trying to provoke a confrontation with police.

In Oakland on Monday night, demonstrators left a gathering at City Hall before briefly blocking Interstate 880, trying to march onto Interstate 580, throwing fireworks and assaulting a restaurant waiter with a hammer.

Oakland police used flash-bang grenades and made nine arrests for crimes including assault with a deadly weapon and vandalism.

Los Angeles officials are very sensitive to images of unrest in a city where the 1965 Watts Riots resulted in 34 deaths and 1992 violence following the acquittal of four white officers in the beating of black motorist Rodney King left 55 people dead and thousands injured.

The LAPD has spent years building relationships in the black community and it's now working with African-American leaders to head off more serious violence. More than 300 police officers responded to the Crenshaw demonstration and they were intentionally slow to directly engage protesters to allow a peaceful end to the demonstration.

Earl Ofari Hutchinson, president of the Los Angeles Urban Policy Roundtable, a south Los Angeles-based community activist group, said the department's response demonstrated the progress that's been made.

"They didn't wade in with stun guns and billy clubs, shooting up the joint, which might have happened 20 years ago," Hutchinson said. "I think that's a sign they've learned a few things."

Los Angeles Police Commissioner John Mack, a former president of the Los Angeles Urban League, said the public needs to differentiate between the troublemakers and the peaceful demonstrators.

"It's important we don't get carried away and get so focused on the few, who in my opinion clearly were not a part of the organized group and had their own agenda," Mack said. "Quite frankly, I'm not so sure that all of them even cared about Trayvon Martin."

___

Associated Press writer Terry Collins contributed to this report. Tami Abdollah can be reached at http://www.twitter.com/latams

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  • Key Dates In The Trayvon Martin Case

    <strong>Feb. 19, 2012</strong> -- Trayvon Martin, 17, and Tracy, his father, travel from Miami Gardens to Sanford, Fla., to visit the elder Martin's fiancee in her townhome at The Retreat at Twin Lakes. <em>Photo courtesy of <a href="http://www.globalgrind.com" target="_blank">globalgrind.com</a></em>

  • Key Dates In The Trayvon Martin Case

    <strong>Feb. 26, 2012</strong> -- Trayvon Martin is walking to the home of his father's fiancee after purchasing items from a 7-Eleven store in Sanford. George Zimmerman, a neighborhood watch volunteer, spots Martin at approximately 7 p.m. and calls police. "We've had some break-ins in my neighborhood, and there's a real suspicious guy," Zimmerman tells police.

  • Key Dates In The Trayvon Martin Case

    <strong>Feb. 26, 2012</strong> -- Roughly seven minutes after Zimmerman's call to police, authorities receive a 911 call from an individual reporting a fight. During the call, the dispatcher hears a gunshot in the background and sends police units to the location. Responding officers discover that Martin has been shot in the chest. The teen is unresponsive and pronounced dead at the scene. Police find no identification on Martin and label him a John Doe.

  • Key Dates In The Trayvon Martin Case

    <strong>Feb. 26, 2012</strong> -- Questioned by police, Zimmerman informs them that Martin attacked him and he fired his gun in self-defense. Authorities confiscate Zimmerman's 9 mm semi-automatic pistol and take him to the Sanford Police Department for further questioning.

  • Key Dates In The Trayvon Martin Case

    <strong>Feb. 27, 2012</strong> -- Following a lengthy interview, George Zimmerman is released from the police station at approximately 1 a.m. Hours later, Tracy Martin contacts police to report his son missing. Investigators soon connect the dots and inform the elder Martin of his son's death. After receiving treatment from a family doctor, Zimmerman meets with investigators and reenacts the events of the shooting at the crime scene.

  • Key Dates In The Trayvon Martin Case

    <strong>March 8, 2012</strong> -- Tracy Martin holds a press conference, during which he criticizes the investigation into his son's slaying. "We feel justice hasn't been served," Martin tells reporters.

  • Key Dates In The Trayvon Martin Case

    <strong>March 9, 2012</strong> -- Martin family attorney Benjamin Crump tells the Miami Herald he is filing a lawsuit for the release of public records in the case.

  • Key Dates In The Trayvon Martin Case

    <strong>March 10, 2012</strong> -- Members of the New Black Panther Party, contending there has been a "miscarriage of justice," rally outside the Sanford Police Department.

  • Key Dates In The Trayvon Martin Case

    <strong>March 12, 2012</strong> -- Sanford Police Chief Bill Lee holds a press conference, at which he claims that investigators were unable to arrest Zimmerman because he was protected by Florida's "Stand Your Ground" law, which allows residents to shoot someone if they reasonably believe they are being threatened. "There is no evidence to dispute Zimmerman's assertion that he shot Martin out of self-defense," Lee says. In response, Martin's parents, Tracy Martin and Sybrina Fulton, post a petition on the Change.org website calling for State Attorney Angela Corey to prosecute Zimmerman. The petition quickly garners support from multiple celebrities and receives nearly 900,000 signatures the first week.

  • Key Dates In The Trayvon Martin Case

    <strong>March 13, 2012</strong> -- In a letter to U.S. Attorney General Eric Holder, the NAACP expresses doubt in the Sanford Police Department's ability to appropriately handle the investigation, asking the Department of Justice to review the case. "The NAACP has no confidence that, absent federal oversight, the Sanford Police Department will devote the necessary degree of care to its investigation," the letter says. Sanford police announce the completion of their investigation and turn the case over to the State Attorney's Office for Brevard and Seminole Counties. "Trayvon Martin and his family, interested persons, and the public-at-large are entitled to no less than a thorough, deliberate and just review of the information provided, along with any other evidence that may or may not be developed in the course of the review process," State Attorney Norm Wolfinger's office says in a statement.

  • Key Dates In The Trayvon Martin Case

    <strong>March 14, 2012</strong> -- Mary Cutcher, a woman listed in police reports as a witness who heard Martin's shooting, <a href="http://www.wftv.com/news/news/witness-sanford-police-blew-us-teen-slaying/nLSqk/" target="_blank">tells WFTV.com that police took only a short statement from her</a> following the shooting. "[The police] blew us off, and I called back again and I said, 'I know this was not self-defense. There was no punching, no hitting going on at the time, no wrestling,'" says Cutcher.

  • Key Dates In The Trayvon Martin Case

    <strong>March 15, 2012</strong> -- Sanford police issue a statement calling Mary Cutcher's TV interviews "inconsistent" with her sworn testimony. Meanwhile, Zimmerman's father, Robert, tells the Orlando Sentinel that his son has been unfairly portrayed as a racist.

  • Key Dates In The Trayvon Martin Case

    <strong>March 16, 2012</strong> -- Sanford police release eight 911 recordings in the case. One of the recordings includes a voice in the background screaming, "Help, help!" The screams are followed by the sound of a gunshot.

  • Key Dates In The Trayvon Martin Case

    <strong>March 19, 2012</strong> -- The Justice Department and the FBI announce they have opened an investigation into the shooting.

  • Key Dates In The Trayvon Martin Case

    <strong>March 20, 2012</strong> -- State Attorney Norm Wolfinger announces that a Seminole County, Fla., grand jury will review the circumstances of Martin's death.

  • Key Dates In The Trayvon Martin Case

    <strong>March 21, 2012</strong> -- The Sanford City Commission votes "no confidence" in Sanford Police Chief Bill Lee and calls for his resignation.

  • Key Dates In The Trayvon Martin Case

    <strong>March 22, 2012</strong> -- Sanford Police Chief Bill Lee holds a press conference and announces he is temporarily stepping down as police chief because his presence is a "distraction." State Attorney Norm Wolfinger recuses himself from the case and Florida Gov. Rick Scott announces that another state attorney, Jacksonville-based Angela Corey, will be replacing Wolfinger as special prosecutor in the investigation. Meanwhile, Rev. Al Sharpton, Martin Luther King III and other civil rights leaders and politicians hold a justice rally at Sanford's Fort Mellon Park. They demand an arrest in Martin's shooting. An estimated 10,000 people attend the event.

  • Key Dates In The Trayvon Martin Case

    <strong>March 23, 2012</strong> -- President Barack Obama tells reporters that the nation needs to do some "soul-searching to figure out how something like this happens." He adds, "If I had a son, he'd look like Trayvon."

  • Key Dates In The Trayvon Martin Case

    <strong>March 24, 2012</strong> -- Members of the New Black Panther Party offer a $10,000 reward for the "capture" of Zimmerman.

  • Key Dates In The Trayvon Martin Case

    <strong>March 25, 2012</strong> -- Rev. Jesse Jackson speaks in Eatonville and encourages revisions to Florida's "Stand Your Ground" law. "If it's a moment, we go home. If it's a movement, we go to war," says Jackson.

  • Key Dates In The Trayvon Martin Case

    <strong>March 26, 2012</strong> -- Police release new details of the investigation, saying Zimmerman told them Martin punched him and slammed his head into the sidewalk several times. Acting Police Chief Darren Scott takes over as chief of the Sanford Police Department. Thousands of people gather in Sanford to mark one month since Martin was killed.

  • Key Dates In The Trayvon Martin Case

    <strong>March 29, 2012</strong> -- Zimmerman's brother, Robert Zimmerman Jr., tells CNN that medical records will prove his brother was attacked and his nose was broken.

  • Key Dates In The Trayvon Martin Case

    <strong>April 3, 2012</strong> -- Florida State Sen. Chris Smith (D-Fort Lauderdale) announces the formation of a task force to review the state's "Stand Your Ground" law.

  • Key Dates In The Trayvon Martin Case

    <strong>April 8, 2012</strong> -- George Zimmerman launches the website "The Real George Zimmerman" to raise money for his defense.

  • Key Dates In The Trayvon Martin Case

    <strong>April 9, 2012</strong> -- State Attorney Angela Corey announces her decision not to use a grand jury in the Martin investigation. The move eliminates the possibility of a first-degree murder charge.

  • Key Dates In The Trayvon Martin Case

    <strong>April 10, 2012</strong> -- Zimmerman's attorneys, Hal Uhrig (right) and Craig Sonner, announce that they will no longer be representing him.

  • Key Dates In The Trayvon Martin Case

    <strong>April 11, 2012</strong> - State Attorney Angela Corey announces the charging of George Zimmerman with second-degree murder. Zimmerman turns himself in to police and is booked into the Seminole County Jail. Mark O'Mara announces his role as Zimmerman's new attorney.

  • Key Dates In The Trayvon Martin Case

    <strong>April 23, 2012</strong> -- George Zimmerman's new lawyer, Mark O'Mara, enters a not-guilty plea on his client's behalf. Zimmerman is released from jail on a $150,000 bond. Per the conditions of his release, Zimmerman is required to wear a GPS monitoring device.

  • Key Dates In The Trayvon Martin Case

    <strong>April 24, 2012</strong> -- George Zimmerman shuts down his website. According to his attorney, the site raised $200,000.

  • Key Dates In The Trayvon Martin Case

    <strong>April 27, 2012</strong> -- Mark O'Mara launches the website GZLegalCase.com as the official site for Zimmerman's legal case.

  • Key Dates In The Trayvon Martin Case

    <strong>May 8, 2012</strong> -- At Zimmerman's arraignment, Seminole County Circuit Judge Kenneth Lester Jr. accepts his not-guilty plea.

  • Key Dates In The Trayvon Martin Case

    <strong>May 17, 2012</strong> -- Prosecutors release police reports, witness statements, surveillance videos and other evidence in the case.

  • Key Dates In The Trayvon Martin Case

    <strong>June 1, 2012</strong> -- Judge Lester revokes Zimmerman's bond, stating that his ruling is based on concerns that Zimmerman and his wife did not fully disclose their finances at the bond hearing.

  • Key Dates In The Trayvon Martin Case

    <strong>June 3, 2012</strong> -- Zimmerman is returned to jail.

  • Key Dates In The Trayvon Martin Case

    <strong>June 12, 2012</strong> -- George Zimmerman's wife, Shellie, is arrested on one count of perjury.

  • Key Dates In The Trayvon Martin Case

    <strong>June 20, 2012</strong> -- The Sanford city manager fires Bill Lee from the police force.

  • Key Dates In The Trayvon Martin Case

    <strong>June 21, 2012</strong> -- George Zimmerman's legal team releases discovery evidence on their client's website.

  • Key Dates In The Trayvon Martin Case

    <strong>June 29, 2012</strong> -- Zimmerman's second bond hearing is held. The judge does not immediately issue a ruling.

  • Key Dates In The Trayvon Martin Case

    <strong>July 5, 2012</strong> -- Judge Lester grants Zimmerman a higher bond of $1 million.

  • Key Dates In The Trayvon Martin Case

    <strong>July 6, 2012</strong> -- Zimmerman is again released from jail.

  • Key Dates In The Trayvon Martin Case

    <strong>July 19, 2012</strong> -- George Zimmerman relaunches his personal website.

  • Key Dates In The Trayvon Martin Case

    <strong>July 27, 2012</strong> -- George Zimmerman's wife pleads not guilty to perjury.

  • Key Dates In The Trayvon Martin Case

    <strong>Aug. 29, 2012</strong> -- An appeals court grants a request by George Zimmerman's defense team to dismiss Judge Lester from the case.

  • Key Dates In The Trayvon Martin Case

    <strong>Aug. 30, 2012</strong> -- Circuit Judge Debra S. Nelson is assigned the case.

  • Key Dates In The Trayvon Martin Case

    <strong>Oct. 19, 2012</strong> -- Judge Nelson grants a defense motion requesting access to Trayvon Martin's school records and social media posts. The state is also granted access to Zimmerman's medical records.

  • Key Dates In The Trayvon Martin Case

    <strong>Nov. 14, 2012</strong> -- Gov. Scott's "Stand Your Ground" task force concludes its final meeting and recommends no sweeping changes to the law.

  • Key Dates In The Trayvon Martin Case

    <strong>Nov. 20, 2012</strong> -- Former Casey Anthony attorney Jose Baez announces that he is representing Sanford police Detective Chris Serino, the lead investigator in the shooting.

  • Key Dates In The Trayvon Martin Case

    <strong>Dec. 3, 2012</strong> -- A new photo is released showing George Zimmerman with a bloody, broken nose on the night of the shooting.

  • Key Dates In The Trayvon Martin Case

    <strong>Feb. 5, 2013</strong> -- On this day, Trayvon Martin would have turned 18.

  • Key Dates In The Trayvon Martin Case

    <strong>Feb. 26, 2013</strong> -- Martin's parents hold a rally in his memory to mark the one-year anniversary of his death.

  • Key Dates In The Trayvon Martin Case

    <strong>March 26, 2013</strong> -- Zimmerman's defense team releases its witness list of 134 people, including Sanford police officers and 56 unnamed witnesses.