This is part of my ongoing series on Canadian Mass Murders.

On April 6, 1999, at approximately 2:30 p.m., Pierre Lebrun drove into the parking lot of OC Transpo’s St. Laurent Boulevard garage and parked near the supervisor’s office.

He walked inside the building, a Remington Model 760 pump-action rifle in hand, and reportedly yelled, “It’s Judgement Day!” then fired his first round.

The bullet travelled through a steel drum, then a metal locker before fragments hit two men, Richard Guertin and Joe Casagrande. Both injuries were minor and the men ran down a hallway, yelling for someone to call 911.

An announcement went out over the building’s public address system and many of the 150 employees either ran from the building or hid wherever they could. Others thought it was a bad joke and remained in place.

Lebrun followed the two men down the hallway where he shot and killed his first victim, Brian Guay.

He moved through the building and killed Harry Schoenmakers, then made his way to a store room where he killed Clare Davidson and David Lemay.

Finally, he moved upstairs to a loft overlooking the engine room and killed himself.

Like Gamil Gharbi ten years prior, Lebrun’s pockets were filled with ammunition when he committed suicide.

Also like Gharbi, Lebrun carried a list of people he hated and, presumably, wanted dead, along with the names of three people who tried to help him. Nobody on Lebrun’s list were injured or killed.

In less than thirty minutes from the time he entered the OC Transport facility to the time he took his own life, he killed four people. He also spared the lives of at least six others. Nobody knows why he allowed some to live and killed others.

“It’s very curious as to why he selected certain individuals to kill and permitted certain people to live. He could easily have killed many more people,” said Ottawa-Carleton Regional Police Inspector Ian Davidson.

Police investigators and reporters quickly filled in the blanks about Pierre Lebrun’s life.

What they discovered was a man with a stammer who was bullied from early childhood, a quiet man who struggled with depression.

During the 1996 transit strike, Pierre Lebrun went on sick leave rather than walk the picket line with his fellow workers. Despite advice from his doctor, Lebrun was taunted mercilessly by other employees and, in 1997, he punched a co-worker in the face for making fun of him.

OC Transpo fired him, but was forced to re-hire him after the union intervened on Lebrun’s behalf.

Three months before the shooting, Lebrun quit work and headed west to British Columbia, then south to Las Vegas. He lost his severance pay gambling and drove back to Ottawa just before going on his killing spree.

He left a suicide note in his parents’ home.

The most shocking revelation came during the coroner’s inquest, however.

One OC Transpo employee hanged himself about two months after the shooting. In his suicide note, the man admitted knowing about Lebrun’s murderous plans but never reported it.

“Pierre had talked with me at great length about it and where to be for the better shot at the managers… I feel guilty as hell for not telling anyone. Who was I to know if he’d do it or not?”

The autopsy on Pierre Lebrun revealed he was high on marijuana at the time of the murders.