Toronto (CNN) Toronto police have their suspect -- but they're still looking for a motive.

Alek Minassian, the man accused of plowing into pedestrians with a rented van on Monday, was charged Tuesday with 10 counts of first-degree murder.

The 25-year-old is also charged with 13 counts of attempted murder. Authorities said another count of attempted murder likely will be added.

Investigators are still trying to determine the motive behind the attack, which left 10 people dead and 14 hurt. One aspect they will look at is his social media posts and what a man who killed six people with a vehicle in 2014 meant to Minassian.

Minassian, who was wearing a white jumpsuit with his hands cuffed behind him, appeared attentive during the brief hearing. His next court appearance will be a bail hearing on May 10.

Alek Minassian is charged with a total of 23 counts for Monday's van plowing attack.

"Obviously all Canadians continue and will continue to have questions about why this happened, what could possibly be the motive behind it," Canadian Prime Minister Justin Trudeau said Tuesday.

So far, officials aren't calling the attack an act of terrorism. "There would appear to be no national security connection," Canadian Public Safety Minister Ralph Goodale said.

Photos: Van strikes pedestrians in Toronto Photos: Van strikes pedestrians in Toronto Police inspect a van used to strike pedestrians in the North York area of Toronto on Monday, April 23. Multiple people were killed or injured as the van swerved onto the sidewalk, plowing over people in its path. Hide Caption 1 of 8 Photos: Van strikes pedestrians in Toronto An overview of the scene in Toronto. Police arrested suspect Alek Minassian, of Richmond Hill, Ontario, in a white rental van less than 30 minutes after receiving a 911 call about the incident. Hide Caption 2 of 8 Photos: Van strikes pedestrians in Toronto Emergency workers stand around the body of a victim. Hide Caption 3 of 8 Photos: Van strikes pedestrians in Toronto This aerial view shows part of the scene after the van plowed through. Hide Caption 4 of 8 Photos: Van strikes pedestrians in Toronto Coroners wait to transport victims' bodies. Hide Caption 5 of 8 Photos: Van strikes pedestrians in Toronto People embrace at the scene. Hide Caption 6 of 8 Photos: Van strikes pedestrians in Toronto A bystander looks on near a dislodged fire hydrant at the scene. Hide Caption 7 of 8 Photos: Van strikes pedestrians in Toronto A tarp covers a victim's body on Yonge Street at Finch Avenue in Toronto. Hide Caption 8 of 8

But Toronto Police Chief Mark Saunders said, "It's very clear just from a general perspective to say that the actions definitely look deliberate."

The van sped down a busy street Monday with reckless abandon, swerving into the wrong lanes of traffic and careening onto a sidewalk.

Clue emerges from Facebook

Minassian on Monday posted a cryptic message to Facebook minutes before setting off in his rented vehicle, Sgt. Graham Gibson, a homicide detective with the Toronto police, said Tuesday.

Investigators found a Facebook account they believe belongs to Minassian, CNN law enforcement analyst Josh Campbell said.

A message posted on the account earlier Monday read: "All hail the Supreme Gentleman Elliot Rodger!"

Campbell said investigators believe the post refers to the man who killed six and injured 14 in a drive-by shooting and vehicle ramming attack near the University of California Santa Barbara campus in 2014. Rodger later died from an apparent self-inflicted gunshot wound.

Investigators said Rodger was motivated to carry out his attack by a personal grievance related to his immersion in the extremist ideological subculture of men's rights activists, who believe women don't actually want gender equality and have been brainwashed by feminist propaganda.

A mile-long scene of carnage

Minassian was arrested in a white rental van about seven minutes after police received a 911 call, Saunders said Wednesday.

A body lies covered after the chaos near midtown Toronto.

He said Toronto authorities hadn't had previous contact with the 25-year-old suspect. But a US law enforcement official with knowledge of the case said Minassian was known to authorities. Authorities said Minassian left a trail of destruction nearly a mile long, north of midtown Toronto.

"Based on witness accounts, we have a vehicle that started north on Yonge Street from Finch (Avenue) and drove southbound at some point in times on sidewalks, at some point in times driving southbound in northbound lanes," Saunders said, adding that it appeared to be a deliberate act.

'Scene from a war zone'

A coroner waits near the sidewalk where victims lie covered.

Diego DeMatos was one of the good Samaritans who tried to save victims, who Gibson said ranged in age from their 20s to their 80s.

DeMatos said he was driving north on Yonge when he saw the van driving fast southbound. He said he saw the van hit a man and a woman.

"Blood started gushing out of his head, and she was bleeding really badly, too," DeMatos said.

At first, he thought the collision was a hit-and-run. But then he noticed four to five victims on the ground as he drove a few meters farther.

DeMatos said he stopped to help another victim, who was already being aided by someone.

"I went over to try to perform CPR on him. ... He died in our arms," DeMatos said.

"It was like a scene from a war zone. There was garbage cans everywhere, broken bus shelters and mailboxes on the ground."

Hospital officials said 12 of the 14 injured remain hospitalized. Five are in critical condition, three are in serious condition and four are stable.

A dramatic arrest

Cellphone video obtained by CNN partner CTV appears to show a tense standoff with a suspect after the incident. Police have not said whether the person in the video was Minassian.

The footage appears to show a man standing in front of a white van with a damaged front bumper. The man is yelling and extending one arm, pointing an object at an officer standing behind a black car.

The officer has his weapon drawn and pointed at the man. The officer slowly steps toward him and yells "Get down, get down!"

Later in the video, the man is seen on the ground and the officer is cuffing his hands behind him; the object can be seen lying on the ground off to the side.

As for whether the suspect had a weapon, "There's nothing that indicates he has a gun," Saunders said.

Remembering the victims

Details are starting to emerge about some of the 10 people killed.

Anne-Marie D'Amico had worked at the annual Rogers Cup tennis tournament since she was 12 years old, Tennis Canada said.

Anne-Marie D'Amico was well known in the Canadian tennis community.

"Anne-Marie lived for working at Rogers Cup and seeing her fellow volunteers each summer," Tennis Canada Vice President Gavin Ziv said.

"The tournament was such a large part of her life, and we were so lucky to have her on our team each summer. Her passion for Rogers Cup was contagious, and we are honored to let the world know what an amazing person she was and the great things she did for others."

Jordanian national Munir Abdo Habib al-Najar, who was in Canada visiting one of his children, also died in the attack, the Jordanian Ministry of Foreign Affairs said.

Trudeau offered his condolences to the families of the victims and also thanked first responders, who "faced danger without hesitation.

"Their efforts no doubt saved lives and prevented further injuries."