In his now-deleted Facebook post that went up minutes before the attack, Minassian wrote, according to police, "The Incel Rebellion has already begun! We will overthrow all the Chads and Stacys!"
Here's a closer look at some of the terms Minassian used:
"Incel": Short for "involuntarily celibate." The top definition on Urban Dictionary states that "incels" typically blame women for a lack of sexual activity. The definition reads, in part, "a person (usually male) who has a horrible personality and treats women like sexual objects."
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"Chad" and "Stacy": Both slang terms have been used online to refer to people with active sex lives.
Elliot Rodger: The man who killed six UC Santa Barbara students in a 2014 shooting and stabbing rampage. In his post, Minassian referred to Rodger as "the Supreme Gentleman." Rodger had also used the phrase "incel" in online posts to express anger toward women, according to the Associated Press. A 2015 report found that Rodger had researched Nazis and terrorists on the internet.
Because of the Facebook post, similarities have been drawn between Monday's attack and another deadly attack in Canada. In 1989, 14 women were killed in a Montreal classroom after 25-year-old Marc Lepine separated the men and women and then opened fire. He wrote in a suicide note that feminists had ruined his life.
A Toronto police officer said Tuesday that most of the victims in Monday's attack were women but it was not yet clear whether women were deliberately targeted. Police have so far declined to discuss a possible motive.
Prime Minister Justin Trudeau said that he does not consider the attack to be terrorism, saying that the national security threat has not changed.
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The Associated Press contributed to this report.