A passenger was forcibly removed from a United Airlines flight by law enforcement on Sunday after refusing to give up his seat.

According to a person who says they were on the flight, the airline needed room on the overbooked aircraft to reposition crew for another flight. But when it couldn't find enough volunteers, even after offering $800, the airline selected the man and several other passengers to deplane.

A video of the incident shows that the man was dragged off the aircraft by aviation officers after failing to comply with their orders.

Please share this video. We are on this flight. United airlines overbooked the flight. They randomly selected people to kick off so their standby crew could have a seat. This man is a doctor and has to be at the hospital in the morning. He did not want to get off. We are all shaky and so disgusted. #unitedairways Posted by Audra D. Bridges on Sunday, April 9, 2017

In a statement to Business Insider, United Airlines said:

"Flight 3411 from Chicago to Louisville was overbooked. 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."

United CEO Oscar Munoz offered this statement in reaction to the incident:

"This is an upsetting event to all of us here at United. I apologize for having to re-accommodate these customers. Our team is moving with a sense of urgency to work with the authorities and conduct our own detailed review of what happened. We are also reaching out to this passenger to talk directly to him and further address and resolve this situation."

However, the video has quickly made its way around the internet, with much of the criticism falling on United.

According to a statement from the Chicago Police Department, the aviation officers attempted to carry the man off when he fell and hit his head on an armrest. He was taken to Lutheran General Hospital with non-life-threatening injuries.

—Robert in ATL (@Cabbage_the_cat) April 10, 2017