It was a cold, drizzly day on 6 December 1989 when a young man brandishing a firearm burst into a college classroom at the École Polytechnique in Montreal, Canada. The 60 or so engineering students there had little time to react before the men were ordered from the room and the gunman began shooting the women. Six female students were killed instantly, while three more were left injured.

The killer, 25-year-old Marc Lépine, was armed with a legally obtained Mini-14 rifle and a hunting knife: he had earlier told a shopkeeper he was going after "small game". Lépine had previously been denied admission to the École Polytechnique and had been upset, it later transpired, about women working in positions traditionally occupied by men. Before he opened fire, Lépine shouted: "You're all a bunch of feminists, and I hate feminists!" One student, Nathalie Provost, protested: "I'm not feminist, I have never fought against men." Lépine shot her anyway.

The gunman then moved through the college corridors, the cafeteria, and another classroom, specifically targeting women to shoot. By the time Lépine turned the gun on himself, 14 women were dead and another 10 were injured. Four men were hurt unintentionally in the crossfire.

Francine Pelletier, a feminist activist and newspaper columnist at Montreal's La Presse newspaper, describes feeling "totally floored" on hearing about the massacre, but nothing prepared her for the discovery that she was on a list found by police in the killer's pocket. "Nearly died today," it read. "The lack of time (because I started too late) has allowed these radical feminists to survive."

Immediately after the shootings, various media commentators and quasi-psychologists proclaimed that Lépine was a madman and that the women just happened to be in the way, as opposed to being specifically targeted. A psychiatrist at the Hôtel-Dieu hospital in Quebec was quoted in La Presse as saying that Lépine was "as innocent as his victims, and himself a victim of an increasingly merciless society". "This was a period of a significant growth in men's rights groups," says Martin Dufresne, founder of Men Against Sexism, a group active at the time of the massacre. "But the public felt too uncomfortable with the political explanation."

Police refused to go public with the killer's suicide note, arguing at a press conference that it might inspire copycat killings. It was this downplaying of Lépine's true motives that made Pelletier determined to get hold of it. Months later, she was sent a copy in the post, anonymously.

"Would you note that if I commit suicide today it is not for economic reasons … but for political reasons," it read. "Because I have decided to send the feminists, who have always ruined my life, to their Maker … I have decided to put an end to those viragos."

Mélissa Blais, a lecturer and doctoral student at the University of Quebec, is the country's leading scholar on the topic of the massacre and its anti-feminist context. She interviewed a number of women for her research who were active feminists in 1989 and found that many felt responsible for what happened at Montreal. "Afterwards, they chose to be silent to avoid further attack.

"When I became a feminist, around the year 2000, I was puzzled to see that some were still reluctant to talk in political terms about the attack. It seemed as though the most efficient way to dismiss the feminist explanation was to reduce everything to the psychology of a single mad man."

Pelletier agrees that Lépine's act was highly political and believes he knew exactly what he was doing that day. "I always felt those women died in my name. Some of them probably weren't even feminist," she says, "they just had the nerve to believe they were peers, not subordinates of their male classmates

The pro-choice movement was galvanising at the time of the massacre. Six months earlier, a Quebec woman, Chantale Daigle, had scored an important victory by overturning an injunction, obtained by her violent ex-partner, at the Canadian supreme court, preventing her from ending a pregnancy. More than 10,000 women demonstrated in Montreal streets in support of Daigle.

The massacre spurred many campaigns to end male violence and there was much international solidarity. I was part of a group that organised a vigil two days later at Trafalgar Square in London. But, says Pelletier, the effect on the women's movement in Canada was profound.

"I was one hell of a disillusioned little feminist on 6 December 1989. It had all been too easy," she says. "What we realised after the massacre was that there had been a quiet and growing resentment from many men towards feminists, and for us, a huge price to pay for all that we had achieved."

I recently spent some time in Montreal and found a vibrant and growing feminist movement, with older women determined to mentor younger generations and encourage a return to the radicalism that was typical of Canadian feminism before 1989, when the feminist movement was characterised by the formation of father's rights organisations and their refusal to accept that men had institutional power and privilege over women.

In Canada, 6 December is a Day of Remembrance and Action on Violence Against Women and the 23rd anniversary of the atrocity. There will be protests, celebrations and tears as the dead are remembered. As the late feminist writer Andrea Dworkin said: "It is incumbent upon each of us to be the woman that Marc Lépine wanted to kill. We must live with this honour, this courage. We must drive out fear. We must hold on. We must create. We must resist."