The boy’s charges this week were upgraded to include terrorist activity, the Royal Canadian Mounted Police and the Toronto Police Service said in a joint statement.

"For me, incels are an online community of mostly heterosexual men and their self-worth is defined by what they would see as physical and sexual inadequacy," Horgan told USA TODAY.

Many incels embrace a misogynistic worldview and embrace the "violent subjugation of women," Horgan said.

While most of the activity incels embrace stays online, Horgan added some have engaged in public violence.

"It's a set of beliefs that gives meaning and justification and direction and importance to what incels do and the fact that incels are aspiring to change things up in a bigger, broader ideological sense, that's, for me, what make it a classic example of terrorism," he said

"Where things started to change was that I think incels began to look for a sense of what was responsible for all of that," Horgan said

Horgan said Rodger became a "lightning rod" for the incel community

The transition from online activity to real-world activity was "stark," Horgan said. 

"The online incel community is a fascinatingly complex and disturbing place," Horgan said. 

"On behalf of the Homicide detectives tasked with bringing justice to the victims of these crimes, I would like to thank our partners at the Integrated National Security Enforcement Team for their efforts on this case," said Toronto Police Service Inspector Hank Idsinga said in a statement regarding February's stabbing