Shortly before a rented van ploughed into a crowd of pedestrians in Toronto, killing 10 and wounding 14 others, a short and cryptic message was posted on the Facebook account of Alek Minassian, the man accused of carrying out the attack.

The post referred to another mass killer – Elliot Rodger, who shot dead six people and wounded 13 others in Isla Vista, California, in 2014 – and said that the “incel rebellion has already begun. We will overthrow all the Chads and the Stacys”.

Minassian’s Facebook account has since been deleted and police have yet to suggest a motive for the attack, but the post appeared to connect the alleged killer with the so-called “incel” movement, which has made collective sexual frustration the basis for a deeply misogynistic online subculture.

Incel stands for “involuntary celibate”, and the people who identify with the label are almost exclusively male. On incels.me, the subculture’s leading online forum, an incel is described as someone who “can’t have sex despite wanting to”, and is thus also denied the pleasures of relationships. (In incel lingo, sexually successful men are known as “Chads”, and attractive women are called “Stacys”).

Self-identified incels have used the internet to find anonymous support and develop an ideology whose central belief is that the modern world is unfairly stacked against awkward or unattractive heterosexual men.

Incel websites argue that society is set up so that some men have numerous sexual partners, others have none and women get to take their pick in what is often described as a “sexual marketplace”.

Such theories are often buttressed with half-understood theories about evolution, psychology and genetics. And at their heart is a belief that denying men sex is unjust.

As in other reactionary subcultures that reject consensus liberal beliefs, those who take on the incel creed are said to have taken “the red pill” – referring to the scene in the science fiction movie The Matrix where the protagonist chooses to leave his illusions behind.

Frequently such ideas lead to a generalized bitterness towards women. Indeed, the big incel hubs are often viciously misogynistic and regularly feature calls for rape or other violence.

Even the free speech bastion Reddit was forced last year to ban the largest incel subreddit for inciting hate (another subreddit, incelTears, continues to chronicle the excesses of incel culture online).

Some with this mindset take it upon themselves to commit horrendous violence. In videos and a manifesto, the Isla Vista shooter Elliot Rodger justified his own mass homicide in 2014 by presenting it as revenge for his own romantic rejections, and the fact that at 22, he was still a virgin.

Rodger was subsequently adopted by some incels as a hero, and being made into the quasi-ironic figurehead for a “beta uprising”, when sexually unsuccessful men would engage in armed revolt against all of the Chads and Stacys.

Behind the layers of irony and disavowal, then, some incels have constructed a kind of violent, insurrectionary rhetoric from romantic failure and the belief that they are owed sex.

It’s possible that this mindset has influenced another lonely man in Toronto to commit mass murder.

The nature of social media still leaves some room for doubt as to whether the message is genuine, or whether it was really posted by Minassian – and internet trolls have previously misled the media following mass killings with false claims.

Moderators on incels.me were quick to disavow him. One post said Minassian “has never posted on Incels.me. As far as we are concerned, no one on the forum heard of him before these latest news.”

But elsewhere on the site, some users appeared to be defending the attacker. One post castigated other forum users for their squeamishness under the title, “most of you guys are all talk”.