On Monday morning, some of the lockers still had bullet holes in them.

Students filed in at the bell, but the beginning of the day was eerily quiet at Brampton Centennial Secondary School.

As classes got underway, the voice of principal William Springle came over the public address system: “In this earthly existence,” he said, “we may never unravel the mystery that led to the tragedy that befell us last week.”

Then normal activities resumed.

The previous Wednesday — May 28, 1975 — 16-year-old Michael Slobodian walked into the high school carrying two rifles in a black guitar case. Within five minutes, Slobodian had killed two people and wounded 13 more. He then shot himself fatally in the head with a .444-calibre bullet.

The attack left Brampton stunned. Apart from Springle’s speech, there was little official recognition of what had happened in the months and years to come. Many coped with the trauma in silence.

For 40 years, Slobodian’s rampage rippled through the lives of people who were there that day, leaving scars and steering fates. Some wrote songs about it, others wrote plays. Some chose their careers because of it, others their homes. Many say they suffered post-traumatic stress. Others say they emerged from the tragedy stronger.

It was just the second high school shooting in Canadian history, and it remains the bloodiest.

On Thursday, May 28, many of these people will gather at Centennial for a memorial ceremony.

“A lot of us have never even spoken about it in 40 years,” said Pam Hand, who as a Grade 9 student watched in horror while Michael Slobodian put a rifle to his head and pulled the trigger. “There’s a lot of people who need to do a lot of healing.”

Today, the tragic pattern of school shootings is familiar. Columbine may be the most famous, but at least a half-dozen more have become bywords in the last 30 years: Dawson College, École Polytechnique, Concordia, C.W. Jefferys, Virginia Tech, Sandy Hook.

But in 1975, and in Brampton — then still many years shy of its expansion into a suburban boomtown — bloodshed in school hallways was virtually unheard of.

Newspaper accounts from the time, and a dozen Star interviews with former students this year, reveal a community totally unprepared to cope with tragedy and trauma on the scale wrought by Slobodian’s rampage.

May 28 began inauspiciously in the Toronto suburb: blue skies, kids playing hooky. Michael’s English teacher Margaret Wright called home to say he had been cutting class. When he arrived at the family’s bungalow around 10:40 for the mid-morning recess, his mother confronted him about his absences.

This is the only explanation he offered for what he was about to do:

“To Whom It May Concern,” his suicide note began, written in a looping, boyish hand. “My life is now gone to pot. I am going to eliminate certain people from this world. Those people are: Mrs. Wright, Mr. Bronson and any other sucker who gets in my way. I am then going to kill myself so as not to be imprisoned. I am not insane but just strictly fed up with life. I am not getting anywhere and it’s my fault. I love my parents and my family and I know that they love me. Michael Peter Slobodian.”

The killing began in the boys’ washroom. Slobodian loaded his rifles, a .22-calibre semi-automatic and a .444-calibre lever-action, in a toilet stall. Wearing a green beret, he stepped out and shot three students: Michael Gibeault, 19, Richard Shadrach, 16, and John Slinger, 17. Slinger would not survive.

Then Slobodian stepped into the hallway. Lunch break had just begun. Michael began firing wildly.

Many couldn’t believe what was happening. Grade 10 student Sylvia Meister thought Slobodian and his rifles were part of a history lesson at first. Pam Read — now Pam Hand — thought she was witnessing the filming of a commercial. Maureen Abraham — now Maureen Sim — thought someone was setting off cherry bombs.

Reality quickly sunk in: the school’s first floor grew thick with gun smoke and the sound of students screaming. Neil Bristol was standing in the school’s smoking area outside when people came running through the doors, yelling about someone with a gun

Slobodian saw Mrs. Wright, the English teacher, in a doorway — one of his targets. (Michael never reached his other target, science teacher Ross Bronson.) According to reports, she said his name — “Michael” — before he shot her in the chest. Wright would die in hospital.

Then, from down the hall, through a haze of smoke, Pam Read saw Slobodian put a rifle to his head. A forensic assessment later found that he died from “massive destruction of the brain.”

A teacher pulled Scott Thompson, now of Kids in the Hall fame, into a classroom during the shooting. Inside, huddled students plotted to stab any attacker with protractors. Others tried, unsuccessfully, to break windows with chairs. Rumours circulated of more shooters, as many as three, one on each floor.

Police finally told him it was safe to go, more than half an hour after Slobodian killed himself. Thompson remembers students walking in an orderly single file and police telling them not to look left — where Michael’s body was. Thompson and Slobodian lived on the same street and had known each other since childhood.

Outside, students took off running or collapsed on the lawn. A cadre of mothers stood anxiously around the front entrance in housecoats and pyjamas. They had heard the news on the radio.

Thompson says he was in shock; adrenalin made the world cartoonishly vivid. “Everything is so sharp and vibrating … sounds are so crisp … you’re alive in a way that you’re not normally,” he said.

Disoriented, he didn’t go home immediately. When Thompson finally arrived at his front door, his mother was furious. “‘Where the hell were you?’” she said. “‘Why didn’t you call?’”

The next day, when he came down the stairs for breakfast, his mother was reading the newspaper.

“For the first time, it became real. I remember sitting with my mother and crying.”

It would be a rare moment of catharsis. Thompson, like most of the dozen former students interviewed for this story, found their parents and teachers reluctant to discuss the tragedy, wary of “dwelling on it,” keen to move on.

“No one had the words,” said Thompson. “No one had the experience.”

Brenda Weitendorf was injured by shrapnel after a bullet struck a wall behind her. The shot came so close that she also received gunpowder burns.

“They didn’t know about PTSD,” she said. “We got no help. It was almost this taboo thing.”

Sylvia Meister’s left arm was grazed by a bullet in the shooting. Her psychological wounds were much more serious. For years, she says she kept that suffering to herself.

“I was in desperate emotional pain. But I, for some reason, didn’t want to put a voice to it,” she said. “I don’t know if it was discouraged. I just don’t know if it was encouraged, which sometimes has the same result.”

The attempt to soldier on began at school.

“We were preparing for exams and marks, so students came back even though they had a fearful feeling about the school,” said Springle, the principal, reached this week at his home in Erin.

There had been some cleanup over the weekend, but the building still bore physical marks of Slobodian’s attack. Thompson remembers there was still blood behind a water tank in the boys’ washroom.

Sylvia Meister noticed the hole in the wall created by the bullet that grazed her arm.

Several students found Margaret Wright’s classroom especially chilling.

“We tried to go in that day,” said Tracy Reid (née Burt). “But it was really an eerie, cold feeling, and we left.”

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Few people laughed or raised their voices that first Monday, Pam Hand recalled.

“I remember just thinking, ‘It’s so quiet. It’s so, so quiet.’”

As the shock wore off, the silence persisted. Neither the school nor police offered counselling for students who had witnessed the killing.

“I don’t think it was the fault of anyone in particular — that’s just the way it was,” said Lorna McCluskey, who hid in an art supply closet during the shooting. “I guess they thought if we dwelled on it, we would get all depressed.”

Part of the problem in discussing what happened is that it was, and remains, so inexplicable. Slobodian had no obvious mental health problems, no pressing grievances with other students.

There were a handful of faint “warning signs” — he was “quiet”; he joined the local militia in April; he didn’t have many close friends; he dabbled in weed and LSD; he was a keen hunter. In what is perhaps the strangest omen, Slobodian was working on a biology project that was rejected for the science fair because it involved killing frogs, removing their hearts, and then resurrecting the animals by applying electrical shocks to the organs.

Still, many people eventually recognized his sudden eruption for what it was: a mystery.

“I’ve stopped asking myself why he did it,” said Dean Nadon, a student wounded by Slobodian, in a January 1977 interview with the Star. “I’ve come to accept the fact that there are some questions which have no answers.”

With or without an explanation, many former students can’t help reliving the shooting to this day. Scott Gibbons, who carried a wounded female student to the nurse’s office during the attack, has flashbacks whenever he sees a massacre on the TV news.

“It’s visceral,” he said. “You just get that feeling. You just know what it’s like … It’s like when somebody pulls a knife on you — everything goes quiet real fast.”

Sylvia Meister still gets frightened by loud noises.

“I’m quite sure I had PTSD for years,” she said. “I probably just in the last 10 years have gotten past that. But even talking about it now, it’s difficult.”

Scott Thompson still can’t be in a room with balloons — the sound their popping makes is too close to the pop-pop-pop of Michael Slobodian’s .22-calibre rifle.

For some, the memories were too sharp, too painful. Pat Slinger was studying as a mature student at Centennial in 1975. She rushed into Mrs. Wright’s class, Rm. 104, when the shooting started. There she found the teacher with a large chest wound that she couldn’t cover with her hand, she later told the coroner’s inquest. Slinger didn’t know that her son John was bleeding to death in the boys’ washroom.

In the immediate aftermath of the tragedy, the Slingers lobbied publicly for tighter gun controls. But according to a 2008 death notice published in the Globe, the family moved to Alberta in 1976, “haunted” by the killing.

For her part, Brenda Weitendorf transferred to a high school in Mississauga after the attack. Forty years later, she still hasn’t been back to Brampton Centennial.

Weitendorf was willing to talk about her experience. Many others were eager, details spilling out in a flood of bottled-up talk.

But for some, especially those with serious physical injuries, the thought of an interview was too painful.

Dean Nadon begged off. The bullet that killed Mrs. Wright passed through her body and hit him in the hip before lodging near his spine. He very politely said he didn’t feel up to discussing it.

When Slobodian emerged from the bathroom stall with bandoliers of bullets making an “X” across his chest, Michael Gibeault was the first to see him. In 2012, he posted to a Facebook page for people affected by the shooting and described how he took three bullets to the stomach and one to the arm. Decades later, when he was diagnosed with cancer, doctors determined that lead from those bullets was still in his body and contributing to the illness. Gibeault died in 2013.

It can seem insensitive to look for a silver lining in so much tragedy. Some former students felt it was perverse to attribute any good to the shooting that killed Mrs. Wright and hobbled Ernie Nicholls. But others reluctantly acknowledged that living through trauma changed their lives for the better, in oblique but powerful ways.

Twenty years after his pal John Slinger was killed, Brampton musician Bruce Madole finally sat down and wrote a song about what happened. “After The Shooting Stops” is about hard-learned lessons. “I never knew what friends were for until one of mine lay dying,” he sings.

Scott Thompson also channelled the misery of that day. In 1999, on the night of the Columbine shooting, Mrs. Wright appeared to him in a dream and told him to make art out of the tragedy.

“She came to me and said ‘I want you to dance with my bones.’”

Thompson has since penned a darkly comedic screenplay about a suburban school shooting.

“It’s like the worst day of my life, but in some ways it was the best, because I made it through,” he now says.

Others took more direct and practical inspiration from the attack, becoming nurses or cops. Derrick Goobie, a Centennial student in 1975, now works in the Emergency Task Force of the Toronto Police Service, and teaches others how to react to school shootings.

“A lot of times when I’m lecturing, I bring this up, that I was involved with this, and this is what it was like in ’75 and this is what we’re striving to be like today,” he said.

Forty years ago, the students of Brampton Centennial anticipated that the worst day of their lives might be transformed into something other than sheer horror.

The 1975 BCSS yearbook contains some accidentally disturbing moments, like John Slinger and Michael Slobodian alphabetically adjacent to each other in the gallery of headshots.

But the first page carries a message of hope, next to the image of a Canadian flag at half-mast: “On Wednesday May 28, 1975, all of us learned to love one another just a little bit more.”