They survived one of Canada's first high school shootings. Here's what happened next

Warning: This story discusses school violence, sexual assault and suicide.

Ten years ago, Dennis Curley went back to what he calls "the scene of the crime" — back inside Classroom 71 of his Ottawa school.

The St. Pius X High School alumnus was on a personal mission, bent on getting his life back.

For decades, Curley was gripped by nightmares about Oct. 27, 1975, the day a severely troubled classmate named Robert Poulin opened fire on their packed religion class with a shotgun bought at Giant Tiger.

It was one of Canada's first school shootings, and helped pave the way for new federal gun control measures. But it was only one half of what made that day so awful.

That morning, Poulin raped and murdered a neighbour and aspiring doctor, 17-year-old Kim Rabot, who was a student at Glebe Collegiate Institute. He then biked to St. Pius, wounded several more students, and killed himself in the hallway with the gun.

Mark Hough, an 18-year-old with plans to attend law school, was among those injured. While everyone else in Classroom 71 recovered — physically, at least — Hough died in hospital over a month later.

Curley, now in his 60s and a psychotherapist, is thankful "there is no white line around my body," as his professional profile page states.

But Curley struggled for years to understand how "a good man" like Hough could be killed while "a jerk like me" kept on living.

He finally sat down with his own psychotherapist and hit upon the idea of going back to the classroom.

So that's what Curley said he did on Oct. 27, 2015, with the school principal guiding him by the arm.

When it came time to leave Classroom 71, however, Curley froze, seized by the memory of opening the door in 1975 and seeing Poulin's body.

He then fell to his knees and began to cry.

Curley did manage his way out of the classroom, and in the 10 years since, he says he hasn't had a bad dream about the shooting.