04/22/2013 11:56 EDT | Updated 06/22/2013 05:12 EDT

Boston Marathon bombing suspect charged in hospital

A court official says Dzhokhar Tsarnaev, the only surviving suspect in the Boston Marathon bombings, has been charged in hospital with a federal offence, and has made an initial court appearance in his hospital room.

U.S. Attorney General Eric Holder said Monday that 19-year-old Tsarnaev, who was listed in serious but stable condition, was charged with conspiring to use weapons of mass destruction against persons and property resulting in death, and could face the death sentence.

Tsarnaev made his first appearance before a magistrate judge in Beth Israel hospital, according to Gary Wente, circuit executive of the 1st U.S. Circuit Court of Appeals.

Tsarnaev and his 26-year-old brother, Tamerlan, two ethnic Chechen brothers from southern Russia who had been in the U.S. for about a decade, had been identified as suspects in the bombings April 15.

The older brother died early Friday after a gunfight with police in the Boston suburb of Watertown, while his younger brother remained in hospital Monday, unable to speak due to a gunshot wound to the throat.

The White House, meanwhile, said Monday that Dzhokhar Tsarnaev will not be tried as an enemy combatant in a military tribunal because he is a naturalized U.S. citizen.

White House spokesman Jay Carney said he will be prosecuted in the federal court system.

The news came as Massachusetts prepared to mark one week since the tragedy that killed three people and wounded dozens.

On the weekend, U.S. officials said an elite interrogation team would question Tsarnaev, a college student, without reading him his Miranda rights, which guarantees the right to remain silent and the right to an attorney. Such an exception is allowed on a limited basis when the public may be in immediate danger.

Survivors of bombings slowly recovering

Meanwhile, trauma surgeons at Boston Medical Center told reporters on Monday that 15 people hurt in the attack were admitted to their hospital in critical condition, but only one remains.

"Nearly all are walking the halls with physiotherapists," said Dr. Peter Burke, adding they are using walkers to strengthen muscles before they are fitted with prosthetics.

Five of the injured had to undergo amputations below the knee, with another two above the knee.

- Read about how the Boston Marathon attack has created massive health costs

Massachusetts plans to observe a minute of silence Monday to honour the victims and dozens wounded in the bombings. People have been asked to pause at 2:50 p.m. ET, the time the two bombs went off within 10 seconds of each other near the marathon finish line in downtown Boston.

Transit and traffic will come to a stop in Boston, and after the silence, bells on city churches will ring. The White House says President Barack Obama would observe the minute of silence as well.

Canada is holding its own event to honour the victims on the one-week anniversary, with a walk to show solidarity with the people of Boston planned for Monday afternoon in Ottawa. It is being organized by members of the city's running community, who will walk from Parliament Hill to the U.S. Embassy, wearing blue and gold, the official colours of the Boston Marathon.

Organizers say there will be moment of silence led by U.S. Ambassador David Jacobson at the embassy.

Last week's bombings killed three people, including an eight-year-old boy, and wounded more than 170.

A charitable fund set up by the state to cover medical costs for the injured has raised about $2 million so far.

Patrick and Jessica Downes, Boston newlyweds who each lost a leg below the knee, have raised $600,000 toward their goal of $1 million.

Cache of weapons 'dangerous as it gets'

The city's police commissioner says the suspects had such a large cache of weapons that they were probably planning other attacks. Authorities found many unexploded homemade bombs at the scene of the gun battle in the Boston suburb of Watertown early Friday, along with more than 250 rounds of ammunition.

The stockpile was "as dangerous as it gets in urban policing," Boston Police Commissioner Ed Davis said. "We have reason to believe, based upon the evidence that was found at that scene — the explosions, the explosive ordnance that was unexploded and the firepower that they had — that they were going to attack other individuals," he told CBS.

Investigators have not offered a motive for the marathon attack.

The brothers are suspected of killing an MIT campus police officer in Cambridge, Mass., during a getaway attempt Thursday night. They were soon cornered in a residential neighbourhood of Watertown as officers tracked them in a stolen vehicle's GPS.

Police say the suspects fired guns and hurled explosives at police before the younger brother escaped in a car. A transit police officer who was shot remains in critical but stable condition.

- Read about Watertown's reaction after the Boston marathon suspect was arrested

Dzhokhar Tsarnaev was captured Friday night after a homeowner notified police to say he had discovered the suspect in the backyard of a house in Watertown, under the tarp of a boat.

Senator Dan Coats, a member of the Senate Intelligence Committee, said Dzhokhar Tsarnaev's throat wound raised questions about whether he will ever be able to talk again.

The wound "doesn't mean he can't communicate, but right now I think he's in a condition where we can't get any information from him at all," Coats told ABC.

Writing out answers, reports say

It wasn't clear whether Tsarnaev was shot by police or wounded himself.

Tsarnaev was awake and sporadically responding in writing to questions Monday, according to ABC News and NBC News.

"We're told that investigators have been talking to him. He has been writing out his answers," NBC correspondent Chris Pollone told CBC News on Monday.

In the final standoff with police, shots were fired from the boat, but investigators have not determined where the gunfire was aimed, Davis said.

The federal public defender's office in Massachusetts said it has agreed to represent Tsarnaev once he is charged.

In an interview with The Associated Press, the parents of Tamerlan Tsarnaev insisted Sunday that he came to the southern Russian regions of Dagestan and Chechnya from January to July last year to visit relatives and had nothing to do with the Islamic militants operating in the volatile region. His father said his son slept much of the time.

When the two suspects were identified, the FBI said it reviewed its records and found that in early 2011, a foreign government — which law enforcement officials confirmed was Russia — had asked for information about Tamerlan Tsarnaev.

The FBI said it was told that Tsarnaev was a "follower of radical Islam" and was preparing to travel to this foreign country to join unspecified underground groups.

The FBI said that it responded by interviewing Tsarnaev and family members but found no terrorism activity.

No link to Caucasus groups

No evidence has emerged since to link Tsarnaev to militant groups in Russia's Caucasus. The Caucasus Emirate, which Russia and the U.S. consider a terrorist organization, on Sunday denied involvement in the Boston attack.

Chechnya has been the scene of two wars between Russian forces and separatists since 1994. That spawned an Islamic insurgency that has spread throughout Russia's Caucasus, with the worst of the violence now in Dagestan.

- Read Margaret Evans's piece on Grozny's makeover, and the Chechen menace

Despite the violence, Anzor Tsarnaev said Sunday that his son did not want to leave and had thoughts on how he could go into business. But the father said he encouraged him to go back to the United States and try to get citizenship.

In interviews with officials and those who knew the Tsarnaevs, a picture has emerged of the older brother as someone embittered toward the U.S., increasingly vehement in his Muslim faith and influential over his younger brother.

- CBC's Peter Mansbridge takes you Inside the News on the Boston Marathon bombing

The federal Bureau of Alcohol, Tobacco, Firearms and Explosives was tracing the suspects' weapons to try to determine how they were obtained. Neither of the brothers had permission to carry a gun.