Before allegedly killing 10 people with a van in Toronto, Alek Minassian appeared to have posted a message on Facebook that linked him to a toxic online community of misogynists that has become the source of a growing pattern of violence.

The Facebook post, which authorities who spoke with NBC News believe came from Minassian, links Minassian to an online community known as "incels," short for involuntary celibates. The Canadian Broadcasting Corporation also reported that Facebook confirmed the authenticity of the post.

Self-described incels congregate mostly online, meeting in forums and message boards like Reddit and 4chan, and its offshoot site 8chan, to discuss their hopelessness with women in posts that are peppered with racist and misogynistic rants.