Bourque pleaded guilty in the Court of Queen's Bench in Moncton to three charges of first-degree murder and two counts of attempted murder, telling Justice David Smith in a calm voice "I plead guilty" or replying "guilty" as he was asked for his plea on each charge.
Smith told the court the Crown has given notice it will seek three consecutive life sentences on the first-degree murder charges, which means Bourque, 24, would not be eligible for parole for 75 years.
He returns to court Oct. 27 when victim impact statements and pre-sentencing documents will be filed.
Bourque, wearing a plain grey T-shirt, sat emotionless during the proceedings, occasionally looking over toward the gallery. His eyes were barely visible through his shaggy brown hair.
"By pleading guilty you're admitting all the facts and essential elements of the offence," Smith told the packed court. "There will be no trial."
Smith then asked if Bourque understood this, to which he replied, "Yes."
Bourque was recently found competent and mentally fit to stand trial after undergoing a psychiatric assessment. Details of that assessment have been sealed by the court.
Members of Bourque's family refused to comment as they left the court as did Supt. Marlene Snowman, the top officer for the RCMP at the Moncton detachment.
The Crown wouldn't comment and defence lawyer David Lutz wasn't available after the hearing.
Constables Dave Ross, Fabrice Gevaudan and Douglas Larche were killed after responding to a report of a man with firearms in a residential neighbourhood in the northwest area of Moncton on June 4.
Constables Eric Dubois and Darlene Goguen were wounded and later released from hospital.
A regimental funeral for the three slain Mounties saw 2,700 law enforcement officers from across Canada and the United States attend the service at a hockey arena in Moncton.
About 7,000 mourners attended the three-hour service, including Prime Minister Stephen Harper who spoke of a "searing grief" that enveloped New Brunswick after the slayings.
"Together, we struggle for answers," Harper said. "We ask what in God's name happened here and why. We may never know."
Bourque was arrested following a manhunt that spanned 30 hours and brought the city of 69,000 to a virtual standstill.
Neighbours in a quiet west-end neighbourhood of Moncton said Bourque was raised in a well-liked, church-going family. One neighbour said the man's father, Victor, shovelled his driveway and watered his flowers when he was away.
Comments in an affidavit signed by Victor Bourque that was filed in provincial court last month provides a view into his son's behaviour before the shootings.
Just days before, Victor Bourque said his son was ranting against authority and growing paranoid.
In the two-page affidavit, the father said he did not notice any serious mental or emotional problems with his son until about 18 months ago when he said Justin Bourque's condition began deteriorating.
The affidavit was used by Justin Bourque's lawyer in court to request a psychiatric assessment for his client, which was granted by a judge.
Victor Bourque says his son went from living with his parents and six siblings in Moncton to buying a gun, getting kicked out of the house, and becoming depressed and paranoid.
"We were a very close-knit family until Justin was asked by his mother and me to leave the home," he said. "His inappropriate behaviour and his purchase of yet another gun prompted our request."
Victor Bourque said during his visits to the family home after that his son appeared depressed and was emotionally and financially unstable.
"Often, he would pace back and forth while talking about things that made no sense to me or other members of the family," said Bourque.
Bourque said he was unable to reason with his son or calm him down as he drove him to work about two days before the shootings.
"He was ranting and raging against all authority and concerning himself with matters which were well beyond his control and some issues not even relating to Canada," he said.
"This behaviour I can only describe as paranoia."
Victor Bourque said he was with his son about 2 1/2 hours before the shootings. Justin Bourque told his father he was going to work but he never showed up, prompting him to contact his son.
"I called him to ask why he lied to me — he was distant and disrespectful to me on the telephone," he said. "He hung up on me. He had never spoken to me in this fashion before. His tone was very dry and as if it was another person speaking."
A friend of Bourque's said in an interview a couple of days after the shootings that he noticed changes in his friend's behaviour over the last year as Bourque started a Facebook page filled with conspiracy theories.
Before, Trever Finck said Bourque was an outgoing guy who liked camping and hanging out with his friends.
"I just want to know what was going through his head," Finck said at the time.
"What caused such a shift from the guy I knew?"
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