On 6 December 1989, a misogynist who claimed he was “fighting feminism” shot dead 14 women, mostly engineering students, at Montréal’s École Polytechnique. I won’t use the murderer’s name. These men want us to use their names.

The women were Geneviève Bergeron, Hélène Colgan, Nathalie Croteau, Barbara Daigneault, Anne-Marie Edward, Maud Haviernick, Maryse Laganière, Maryse Leclair, Anne-Marie Lemay, Sonia Pelletier, Michèle Richard, Annie St-Arneault, Annie Turcotte and Barbara Klucznik-Widajewicz. They were pioneers – paving a path for themselves and other women in male-dominated fields, facing sexism every day, proving anyone who thinks that women can’t do maths wrong with each successful semester. That is why they were murdered.

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Reporter Shelley Page, then just 24, was sent to the scene. In a soul-searching piece written on the 25th anniversary of the massacre, Page reflected: “Looking back, I fear I sanitised the event of its feminist anger then infantilised and diminished the victims.” She remembers respected Canadian journalists refusing to admit that the massacre was an act of violence against women. She describes her editors’ worry that, as a woman, she wouldn’t be objective in her reporting. She recalls racing around trying to find details to humanise the murderer; she critiques the media’s drive to find any reason besides misogyny for the tragedy.

On Monday night, a man who apparently claims to be part of the “incel rebellion” allegedly rented a van and drove along a 2km stretch of pavement on Toronto’s Yonge Street. “Incels” are an online community of “involuntarily celibate” men who hate women. The attack killed 10 people, predominantly women, and injured at least 13 more.

Moments before the violence, the killer appears to have posted to Facebook about overthrowing “Chads” (good-looking, promiscuous men) and “Stacys” (women who sleep with Chads). He also praised the Isla Vista murderer: a misogynist who, in 2014, released a 137-page manifesto before going on a stabbing and shooting spree in California.

I use the phrase “appears to have posted”, because, although both Facebook and the lead homicide investigator on the case have confirmed that the post appeared on the killer’s Facebook page, it is possible that in the immediate aftermath of the massacre a troll hacked his account, posted the text, then backdated it.

I know this is possible, because, though it seems unlikely, this explanation has been widely proffered as a caution not to start banging feminist drums. While unfounded rumours that the attacker was a jihadist mushroomed across social media, the significance of his apparent affiliation with an online misogynist group has been shushed and spun out of focus. Almost 30 years after the École Polytechnique massacre, we must continue to find any reason for violent misogyny besides violent misogyny.

It’s vital that we keep feminist analysis central to the conversation surrounding the Yonge Street massacre. Why, when men tell us that hatred for women is the root of their violence, don’t we believe them? The École Polytechnique murderer, the Isla Vista murderer, the Yonge Street killer: these were misogynists by their own evidence. If we refuse to look for the common denominator, if these events are always going to be framed in terms of the perpetrator’s mental health or childhood trauma (which, yes, I know, are also often factors), then we can’t confront the radicalisation at the root of it all.

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Talking about the violent misogyny that is likely behind the Yonge Street massacre means delving into an online world that is so stupid and facile that it’s difficult to take seriously.

Here goes: incels are men who can’t get laid. They semi-ironically beatify the Isla Vista murderer. They believe that women are only interested in men who are rich and good-looking. They call women “roasties” because all that sex with Chads has made their labia look like roast beef. Roasties let Chads slap them around the bedroom while they act unattainable and pure to poor, short, weak-chinned incels. (The fact that this ideology is easily disproven by, you know, looking out a window and seeing men of all sizes, shapes and levels of attractiveness hand-in-hand with their partners does not seem to intrude on the incels’ fervour.)

There’s a jokey, ironic-or-is-it tone to incel boards, a tone that Angela Nagle analyses productively in her book Kill All Normies. Sometimes, the posters themselves don’t seem to know whether they’re being serious or not.

Incel boards have reacted to the Yonge Street massacre in different ways, but incels.me has users declaring the date of the attack “an absolutely glorious day”, celebrating the death of D’Amico, and hoping that there’s more violence to come. These spaces are puerile, yet they normalise violent misogyny and have the potential to radicalise socially isolated or vulnerable men. Some of the users are in it for the lulz; some of them are not joking. The latter become the Umpqua Community College murderer, the Isla Vista murderer, the Yonge Street killer. There’s a pattern here, and we can’t keep ignoring it.

In the weeks to come we’ll learn more about the killer’s mental health, about his childhood, his education, his work, his social relationships. These are important windows on to the tragedy. But if involvement in misogynistic online communities is indeed part of the picture here, we need to resist any narrative that would push this into the background. Hatred of women is not a mental illness; it is a widespread and dangerous social problem. It is a problem we need to address before more people die.

• Emer O’Toole is assistant professor of Irish performance studies at Concordia University, in Canada