The Illinois suspects - identified by prosecutors as Jordan Hill, 18, of Carpentersville; Tesfaye Cooper, 18, of Chicago; Brittany Covington, 18, of Chicago; and Tanishia Covington, 24, of Chicago - were arrested and charged with hate crime, aggravated kidnapping, aggravated unlawful restraint and aggravated battery with a deadly weapon. Hill, Cooper and Brittany Covington were additionally charged with residential burglary. Hill also was charged with possession of a stolen motor vehicle, according to the Cook County State Attorney's Office.
The four appeared in Central Bond Court at the Leighton Criminal Courts Building on Friday afternoon. They have not yet entered pleas.
Here's what we know so far about the investigation and how the alleged incident unfolded:
Victim With 'Mental Health Challenges' Reported MissingThe victim, an 18-year-old man who a police official said has "mental health challenges," was dropped off by his parents at a McDonald's restaurant in Streamwood, a suburb northwest of Chicago, on Saturday. They believed he would be spending the night with Hill, his friend and school acquaintance, according to Cmdr. Kevin Duffin of the Chicago Police Department.
Hill allegedly picked up the victim in a stolen van, which the victim assumed was Hill's. The two drove to Chicago's West Side, where they visited with friends for two days and slept in the van overnight, Duffin said.
The victim's parents went to Streamwood police and reported him missing on Monday night. They told police they had not heard from their son since Saturday when they dropped him off, according to the Streamwood Police Department.
Victim Allegedly Bound and Tortured in 'Sickening' VideoOn Tuesday the victim and Hill went to the apartment of the Covingtons, who are sisters. Several hours later, a "play fight" between the victim and Hill escalated, and the suspects bound him and began to assault him, Duffin said.
"That's when racial slurs and [references] to his mental capacity starts coming out," Duffin said at a news conference Thursday. "That's primarily one of the reasons why they were charged with the hate crime."
Video of the incident was posted live on Facebook but was later removed. The social media company said it "does not allow people to celebrate or glorify crimes on Facebook."
The video shows the victim, a white man, with his mouth taped shut as his captors appear to repeatedly assault him.
"It's sickening," Chicago Police Department Superintendent Eddie Johnson said of the incident during a news conference Wednesday. "It makes you wonder what would make individuals treat someone like that."
In the video, someone is heard yelling, "F--- white people." And at one point, the victim was threatened with a knife and told to curse President-elect Donald Trump.
"Say, 'F--- Donald Trump,'" someone is heard saying.
"F--- Donald Trump," the victim says.
'Battered' Victim Escapes, Is Located by PoliceAfter nearly six hours of being tormented by his captors Tuesday, the victim managed to free himself and escape after the suspects left the apartment to confront a neighbor on a lower floor who had complained about the noise they were making, according to Duffin.
The neighbor complained to the Covingtons and threatened to call the police if the noise didn't stop. The sisters were angry about being asked to quiet down, so they left the apartment and went downstairs to kick in the neighbor's door, according to Duffin. That provided the alleged victim with an opportunity to flee the building, Duffin said.
Chicago police officers were dispatched on Tuesday to respond to a damaged property call at the Covingtons' apartment building, stemming from the sisters' kicking the neighbor's door. That's when Officer Michael Donnelly spotted the victim on a street nearby, he told reporters at Thursday's news conference.
The officer said the victim was wearing jean shorts, sandals and an inside-out and backward tank top, despite the frigid temperatures. The man was "bloody" and "battered" when Donnelly approached, he said.
He said he called an ambulance and left the victim with two other officers, then went to investigate at the Covingtons' building. The man was transported to a nearby hospital for treatment, police said.
Suspects Arrested, Charged in 'Brutal Act'While investigating at the Covingtons' apartment, Chicago police said they observed "signs of a struggle and damage to the property and were able to link this evidence to the disoriented male."
Meanwhile, as Streamwood police officers were investigating the victim's disappearance, the parents "began receiving text messages from persons claiming to be holding him captive," the Streamwood Police Department said in a statement. Soon after that, Streamwood police discovered the video on Facebook, and they were informed by the Chicago Police Department that the victim had been located.
The four suspects were arrested Wednesday and charged the next day in connection with what a police official called a "brutal act." In video statements to investigators, the suspects admitted to beating and kicking the victim and making him drink toilet water, police said.
Cook County Judge Maria Kuriakos Ciesil denied public defenders' request for bond in the suspects' court appearance Friday.
Obama Addresses 'Horrific' AttackIn an interview on Thursday with ABC's Chicago station, WLS, President Obama called the alleged incident "horrific" and "terrible."
Obama noted that technology can play a useful role in exposing racism and hatred that still exists in the country.
"Part of what technology allows us to see now is the terrible toll that racism and discrimination and hate takes on families and communities. But that's part of how we learn and how we get better," he told WLS. "We don't benefit from pretending that racism doesn't exist and hate doesn't exist. We don't benefit from not talking about it. The fact that these things are being surfaced means we can solve them."
Victim and Family Trying to HealThe victim's family held a news conference Thursday in Crystal Lake, Illinois. "He's doing well - as well as he could be at this time," the victim's brother-in-law, David Boyd, said. "We're so grateful for all the prayers and efforts that led to the safe return of our brother.
Boyd confirmed that the family is "fully aware of the charges being brought against the offenders." He said that family members have been "overwhelmed and surprised" by the outpouring of support from the public and that they are "trying to stick together" as they "cope and heal."
"We're happy everyone is concerned," he told reporters. "This should never happen."
ABC News' David Caplan, Matthew Foster, Alex Perez, Darren Reynolds, Nadine Shubailat and Jason Volack contributed to this report.