The three deaths were the first Mounties killed by gunfire since November 2007. Two officers were injured, and one of them is still in the hospital
A Facebook page that appears to belong to Bourque contains numerous postings from gun-rights groups, anti-police sentiment and song lyrics.
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"Ask yourself, would you fight for the future of your children or grandchildren, or your family and friends sons and daughters? The answer is: no you're too stupid to know what to fight for, cause we're already losing the silent war you don't wanna believe is happening," an April 7 posting reads.
The last update to the page was made hours before the shooting and quoted a Megadeth song. Below it, after the bloodshed, a friend posted a message: "You knew this wasn't the answer."
Several friends on Facebook of Bourque did not reply to requests for comment.
The suspect is believed to be heavily armed.
An image from the Times and Transcript newspaper showed a man in camouflage with a bandanna around his forehead carrying an assault-style rifle, with another slung over his shoulder. He also appeared to be carrying a backpack.
Codiac RCMP are searching for 24-y-o Justin Bourque of Moncton. Anyone with information call 9-1-1. http://t.co/JCcJyixfce
The suspect appears to have a tactical shotgun on his back with a collapsible stock and shotgun shells strapped to his bottom, said NBC law enforcement analyst Jim Cavanaugh. He also appears to be carrying a sniper rifle, similar to a .308 caliber, and a detachable magazine, he added.
The officers were killed about 7:30 p.m. local time (6:30 p.m. ET) Wednesday. Paul Greene, a spokesman for the Mounties, said in an email to NBC News that the officers, all from the Codiac Regional RCMP, were shot after responding to a call about a man with a gun.
A separate shooting took place near the city of Dieppe, just east of Moncton. Moncton is a city of about 70,000 people three hours up the coast from the border between Canada and Maine.
The last Mountie to die by gunfire, according to an honor roll on the RCMP website, was Constable Douglas Allen Scott, who was shot while responding to a call for assistance involving an impaired driver on Nov. 5, 2007, in Kimmirut, Nunavut.
Two years earlier, four constables were shot to death by a deranged suspect near Mayerthorpe, Alberta, the honor roll says.