A man was violently dragged off of a United Airlines flight Sunday evening after it was apparently overbooked, according to passengers who were on the plane.

As The Courier Journal reports, a United spokesperson confirmed in an email Sunday night that a passenger had been taken off a flight in Chicago.

"Flight 3411 from Chicago to Louisville was overbooked," the spokesperson said. "After our team looked for volunteers, one customer refused to leave the aircraft voluntarily and law enforcement was asked to come to the gate. "We apologize for the overbook situation. Further details on the removed customer should be directed to authorities."

Passengers were told at the gate that the flight was overbooked and United, offering $400 and a hotel stay, was looking for one volunteer to take another flight to Louisville at 3 p.m. Monday. Passengers were allowed to board the flight, Bridges said, and once the flight was filled those on the plane were told that four people needed to give up their seats to stand-by United employees that needed to be in Louisville on Monday for a flight. Passengers were told that the flight would not take off until the United crew had seats, Bridges said, and the offer was increased to $800, but no one volunteered.

Then, she said, a manager came aboard the plane and said a computer would select four people to be taken off the flight. One couple was selected first and left the airplane, she said, before the man in the video was confronted.

Classic @United overbook #flight3411 and decided to force random passengers off the plane. Here's how they did it: pic.twitter.com/UaiSKz2bHD — Stephen (@stephenlaca) April 10, 2017

Bridges said the man became "very upset" and said that he was a doctor who needed to see patients at a hospital in the morning. The manager told him that security would be called if he did not leave willingly, Bridges said, and the man said he was calling his lawyer. One security official came and spoke with him, and then another security officer came when he still refused. Then, she said, a third security official came on the plane and threw the passenger against the armrest before dragging him out of the plane.

"Everyone was shocked and appalled," Bridges said. "There were several children on the flight as well that were very upset."