Shortly before Alek Minassian allegedly plowed a rental van into pedestrians in Toronto, he apparently posted a cryptic message on Facebook, suggesting he had frustrations toward women, authorities said.
In the message, Minassian allegedly praised a man who vowed to "destroy" women who rejected him.
"All hail the Supreme Gentleman Elliot Rodger!" the message said, according to CNN law enforcement analyst Josh Campbell.
The post was an apparent reference to the California killer who carried out a "day of retribution" four years ago.
10 counts of first-degree murder
Toronto police said Tuesday that Minassian posted the message just before he allegedly took off in his vehicle. Sgt. Graham Gibson, a homicide detective, said Minassian's feelings about Rodger will be part of the investigation.
After posting the message, police say Minassian targeted pedestrians with his van, killing 10 people and leaving 14 injured. He was charged with 10 counts of first-degree murder and 13 counts of attempted murder. Another charge of attempted murder is being considered, officials said.
Authorities are looking into a possible grudge against women as a motive, but the investigation is still in the preliminary stages.
Facebook has since taken down the post, which read in part, "The Incel Rebellion has already begun! We will overthrow the Chads and the Stacys! All hail the Supreme Gentleman Elliot Rodger."
Incel means involuntarily celibate people who believe they are denied sex by women due to their looks, social inadequacies, awkwardness and demeanor, according to change.org, where a user launched a petition to ban the incel community from Reddit.
Reddit shut down the online community of incels in November, according to The New York Times.
Gibson said they are looking at all aspects of the investigation, including the content of the post and the suspect's stance on Rodger.
Part of the investigation will include whether the suspect was motivated by his frustrations with women, Gibson said. While his victims are "predominantly female," he said, it's unclear whether he was bypassing men and targeting women.
"We have no evidence of that at this stage," Gibson said.
Minassian, 25, is from the Toronto suburb of Richmond Hill, police said. Toronto authorities said they had no previous interactions with him, but a US law enforcement official said he had been known to authorities.
A former classmate said the suspect often succumbed to peer pressure -- such as running down a hallway shirtless when dared by other students. The classmate, who didn't want to be identified, said they bonded during special-needs classes in school.
The classmate said Minassian was very self-deprecating. "If you put him down or disrespected him or insulted him, he would agree with you," the classmate said.
Minassian had severe anxiety when interacting with females and would freeze, unable to respond, the classmate said. "He was genuinely terrified with interacting verbally or physically at all, except for his mother," the classmate said.
Another former classmate said Minassian was odd and kept to himself, but "he was always smiling." Minassian served in the Canadian armed forces last year, from August to October, a spokeswoman told CNN.
"He did not complete his recruit training and requested to be voluntarily released from the CAF after 16 days of recruit training," the Department of National Defence said. "For privacy reasons, we will not comment further on Alek Minassian's service in the CAF."
Minassian was arrested about seven minutes after police got a 911 call about the deadly rampage, Toronto police Chief Mark Saunders said.
He may have engaged in a tense standoff with police before his arrest. A cell phone video obtained by CNN partner CTV shows a man standing in front of a white van with a damaged front bumper, but officials haven't confirmed whether the man is Minassian.
The man yells and extends one arm, pointing an object at an officer standing behind a black car.
The officer, his weapon drawn, points at the man. The officer slowly steps toward him and yells "Get down, get down!"
Later in the video, the man is on the ground as the officer cuffs his hands behind him. The object, which Saunders said was not a gun, also drops to the ground.
Authorities haven't released a motive. But, so far, officials are not calling this an act of terrorism. "There would appear to be no national security connection," Canadian Minister of Public Safety Ralph Goodale said.
Rodger killed six people and injured 14 others in a stabbing, shooting and vehicle-ramming attack in 2014 near the University of California, Santa Barbara campus.
Investigators noted that Rodger was motivated by a personal grievance related to the extremist ideological subculture of men's rights activists. Supporters believe women don't want gender equality and have been brainwashed by feminist propaganda.
After his rampage, Rodger died from an apparent self-inflicted gunshot wound.
CORRECTION: A previous version of this story incorrectly stated the date of a Toronto police news conference.