Updated at 4:15 p.m. ET

Four people have been charged with hate crimes for allegedly carrying out an assault, live-streamed online, in which a man was tied up, hit and cut with a knife by several assailants.

Authorities say the victim, who had been reported missing before the attack, has "mental health challenges." He was encountered by police on Tuesday evening and is recovering in the hospital.

"There was never a question whether or not this incident qualified to be investigated as a hate crime," Police Superintendent Eddie Johnson said at a news conference Thursday afternoon, citing the victim's mental capacity, race and other factors. "The actions in that video are reprehensible."

The Facebook Live stream showing the attack has been deleted. But multiple outlets have posted videos they identify as archives of the stream, recorded by a woman who frequently turns the camera on herself. The clips show multiple people taunting, threatening and hitting a man who is tied up in a corner. At least once, a man uses a knife to cut the victim's hair, cutting into his scalp.

On the video, the assailants, who are black, say "F*** Donald Trump" and "F*** white people." They force the victim, who is white, to say "F*** Donald Trump," as well.

The four people accused of the crime have each been charged with a hate crime, aggravated kidnapping, aggravated unlawful restraint, and aggravated battery with a deadly weapon, according to the Cook County State's Attorney's office. Other charges include burglary, robbery and possession of a stolen motor vehicle.

As for the remarks about President-elect Donald Trump, police Cmdr. Kevin Duffin said at a news conference late Wednesday that investigators are working to determine whether the statements are "sincere or just stupid ranting and raving."

Chicago police found the victim in distress on the street before they were aware of the existence of the Facebook live stream, authorities said at the news conference. The four suspects were arrested after police were called to a residence near where they'd found the man and then connected the incident and the location.

The victim, a resident of a Chicago suburb, apparently spent at least 24 hours in the company of his alleged assailants — one of whom he knew from school, police say. He had been reported missing on Monday. Police say he traveled into the city with his acquaintance in a stolen van.

A GoFundMe account for the victim has been set up; a public relations representative for GoFundMe says the website will be working with the campaign organizer to ensure all money raised reaches the victim.

At Wednesday's news conference, Johnson highlighted the "brazenness" of the assailants, for not just carrying out the attack but broadcasting it "for all to see."

"It's sickening," he said. "It makes you wonder what would make individuals treat somebody like that. I've been a cop for 28 years — I've seen things that you shouldn't see in a lifetime — but it still amazes me how you still see things that you just shouldn't [see]."

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