Several disturbing videos posted to social media Sunday show a man being violently dragged off a United Airlines plane out of Chicago after the company said they needed his seat for its crew.

Video posted to social media shows the man screaming as security personnel pry him out of his chair, causing his head to bash against an armrest. He’s then dragged down the aisle on his back as horrified witnesses film on their phones and scream out in disgust.

@united @FoxNews @CNN not a good way to treat a Doctor trying to get to work because they overbooked pic.twitter.com/sj9oHk94Ik — Tyler Bridges (@Tyler_Bridges) April 9, 2017

“My God, what are you doing? No, this is wrong!” one woman cries as she watches the man being dragged past her feet. “Oh my God look at what you did to him! Oh my God!”

Someone else describes the man as having “busted his lip.”

Audra D. Bridges, who posted a video of the encounter to Facebook, told The Courier-Journal that airline staff were looking for one volunteer to give up a seat before the flight to Louisville, Kentucky, boarded. Passengers were offered $400 and a hotel stay.

After the flight boarded, staff announced that they needed four people to volunteer to give up seats so that United employees who needed to be in Louisville Monday could take them. The amount was increased to $800, she said, and passengers were told the plane wouldn’t leave until four people volunteered.

When nobody offered, staff announced a computer would select four people. One couple cooperated and left. The man in the video was also selected.

One Twitter user who also posted video of the dramatic ordeal said the airline sought four volunteers “for personnel that needed to be at work the next day.”

In the videos, an upset woman is heard suggesting that the pilots rent a car and drive to Louisville instead.

@United overbook #flight3411 and decided to force random passengers off the plane. Here's how they did it: pic.twitter.com/QfefM8X2cW — Jayse D. Anspach (@JayseDavid) April 10, 2017

In a statement, the airline apologized for what they initially claimed was an “overbook situation.”

“After our team looked for volunteers, one customer refused to leave the aircraft voluntarily and law enforcement was asked to come to the gate,” the airline said in a statement. “We apologize for the overbook situation. Further details on the removed customer should be directed to authorities.”

On Tuesday, United told USA Today that they were not actually overbooked, but needed the seats for crew members.

The company CEO also released a statement on Twitter apologizing for having to “re-accommodate these customers.”

United CEO response to United Express Flight 3411. pic.twitter.com/rF5gNIvVd0 — United (@united) April 10, 2017

In an email to United employees, obtained by ABC News, Munoz said he was “upset” by the incident, but cast blame on the customer.

“While the facts and circumstances are still evolving, especially with respect to why this customer defied Chicago Aviation Security Officers the way he did, to give you a clearer picture of what transpired, I’ve included below a recap from the preliminary reports filed by our employees,” Munoz wrote in the email, which included a five-point summary of what transpired.

“I do, however, believe there are lessons we can learn from this experience, and we are taking a close look at the circumstances surrounding this incident,” he added. “Treating our customers and each other with respect and dignity is at the core of who we are, and we must always remember this no matter how challenging the situation.”

United CEO email to employees obtained by ABC's @Shahriar44R: "there are lessons we can learn from this experience" pic.twitter.com/N1TbohuRc3 — Michael Del Moro (@MikeDelMoro) April 10, 2017

The Chicago Police Department told The Huffington Post that Chicago’s Department of Aviation Police handled the incident. In a statement, the Department of Aviation Police said, “The incident on United flight 3411 was not in accordance with our standard operating procedure and the actions of the aviation security officer are obviously not condoned by the Department. Th at officer has been placed on leave effective today pending a thorough review of the situation.”

The Chicago PD also released a statement calling the man in the video “irate” and saying that he fell.

Bridges said on Facebook that the booted passenger didn’t want to get off because he is a doctor who had to be at a hospital in the morning.

“He did not want to get off. We are all shaky and so disgusted,” she wrote.

Another video posted to Twitter by @Tyler_Bridges appears to show the man back on the plane after he was removed. The man can be heard saying, “I have to go home.” Other videos posted online showed the man clearly bleeding and disoriented on the plane.

According to The Courier-Journal, some passengers asked to get off the plane after a medical crew entered the aircraft to help the man, she said.

In response to the videos, some are vowing to never do business with the airline again. The incident also comes just two weeks after the company found itself in hot water for refusing to allow three girls to board a flight because they were wearing leggings.

Hey @united I'm thinking your overbooked issue is gonna fade away. You may have under-booking issues tho. Never flying #UnitedAirlines ever — Silver (@SilverPedalist) April 10, 2017

I would not want to be @united Airlines right now. — Ari Fleischer (@AriFleischer) April 10, 2017

An astonishingly nasty move for @united — "We screwed up and overbooked flight, so oh hey there's a guy, let's beat him and drag him off." — Chuck Wendig (@ChuckWendig) April 10, 2017

.@united Do not fly @United. They are Spirit with higher prices and less shame. — Kimberly N. Foster (@KimberlyNFoster) April 10, 2017

This is horrifying. It seems the world should rework its "treating people as humans" algorithm. And @united needs to redefine "voluntarily." https://t.co/5gIJpeATp0 — Amanda Morin (@AmandaMorin) April 10, 2017

@Tyler_Bridges @united @FoxNews @CNN "Welcome aboard of United Airlines. Unless we screw up with overbooking, then we'll just drag you out like an animal." #DontFlyUnited — Emil K (@EmilKirakosyan) April 10, 2017

United clarified on Tuesday that the plane was not technically overbooked in a statement to USA Today. This article has been updated accordingly.