The Canadian man accused of mowing down pedestrians with a rented van in northern Toronto last month has been charged with three additional counts of attempted murder.

Standing quietly in an orange jumpsuit, Alek Minassian, 25, appeared in court in Toronto via video link this morning as a judge announced the new charges. Minassian now faces 10 counts of first-degree murder and 16 counts of attempted murder related to the April 23 attack.

Minassian is scheduled to appear in court again on September 14 via video link.

Minassian was arrested and taken into custody after the attack, which killed 10 people and injured 16 others, according to the Toronto Police Service. Police initially said 13 people had been wounded, but an ongoing investigation revealed that three others had also been injured.

Police said Minassian went to a Ryder truck rental facility just north of Toronto where he rented a "paddle-style" white van the morning of April 23. That afternoon, he allegedly drove the van to Yonge Street and Finch Avenue in Toronto's bustling North York neighborhood, where he began ramming into pedestrians on the roadway and sidewalk, police said.

Minassian then allegedly drove south down Yonge Street for nearly one and a half miles, striking more pedestrians near Sheppard Avenue, police said. The battered vehicle finally stopped just off Yonge Street on Poyntz Avenue, according to authorities.

Minassian's neighbors in the Toronto suburb of Richmond Hill described him as quiet and odd. Neighbors at the time told ABC News they had seen Minassian around -- including one neighbor who said he would walk the neighborhood with a laser focus but not engaging with anyone around him -- but had never spoken to him.

Just minutes before the April 23 attack in the capital city of the province of Ontario, Minassian allegedly wrote a chilling post on Facebook about an "incel rebellion," an abbreviated term for "involuntary celibate," authorities said.

In the single post on his Facebook account, which was taken down soon after the attack, Minassian praises Elliot Rodger, a 22-year-old student at the University of California, Santa Barbara, who killed six people and wounded others before killing himself in his car four years ago.

The Facebook post read: "The Incel Rebellion has already begun! We will overthrow all the Chads and Stacys! All hail the Supreme Gentleman Elliot Rodger!"

Rodger had lamented his "loneliness" in several YouTube videos, a blog and a 137-page manifesto created before the 2014 rampage. In his writings, Rodger had appeared baffled -- and angry –- about why women were "repulsed" by him because he considered himself the "ultimate gentleman."

The terms "Chad" and "Stacy" in the Facebook post allegedly written by Minassian are references often used on anonymous internet forums, like Reddit and 4chan, where the online community of self-declared "incel" men has been known to congregate. "Chad" apparently refers to a man who has success with women, while "Stacy" is a seemingly unattainable woman who rejects "incels."

At a press conference last month, Toronto Police Service Homicide Det. Sgt. Graham Gibson confirmed to reporters that Minassian is alleged to have posted the "cryptic message" on Facebook. Gibson also said it was "fair to say" that the victims in the attack were "predominately female," ranging in age from their mid-20s to 80s.

But there's no evidence so far that Minassian was specifically targeting women when he "deliberately" drove into pedestrians in Toronto's bustling North York neighborhood, Gibson said.

Gibson wouldn't say whether there is evidence to suggest the suspect was frustrated with or held grudges against women, but the detective sergeant said it's something investigators will look into. He also declined to comment on whether there's reason to believe Minassian is mentally ill.

A day after the attack, Canadian Prime Minister Justin Trudeau said during a press conference that investigators at the time "have no reason to suspect that there is any national security element to this attack."

"Obviously, all Canadians continue and will continue to have questions about why this happened, what could possibly be the motives behind it,” Trudeau told reporters in Canada's capital, Ottawa.

ABC News' Andrew Fies, Ben Gittleson, Alex Hosenball, Tom Llamas and Gerry Wagschal contributed to this report.