The disturbing scene captured on cellphone videos by United Airlines passengers on Sunday went beyond the typical nightmares of travelers on an overbooked flight.

An unidentified man who refused to be bumped from a plane screamed as a security officer wrestled him out of his seat and dragged him down the aisle by his arms. His glasses slid down his face, and his shirt rose above his midriff as uniformed officers followed.

An airline employee came on board and said United needed four people to get off, Mr. Bridges said, adding that the airline had by then increased its incentive to an $800 voucher. The airline later said that it offered up to $1,000 in compensation.

Mr. Hobart, the United spokesman, confirmed that United sought passengers willing to give up their seats with compensation but that none stepped forward.

Another United employee told passengers that the plane would not leave until four people got off, Mr. Bridges said. The employee specified that the airline had four United employees who needed to get to Louisville, he said.

Four passengers were selected to be bumped, and three left without incident, Mr. Hobart said.

Mr. Hobart would not say whether the bumped passengers were chosen by a computer, an employee or some combination of the two. But factors can include how long a customer would have to stay at the airport before being rebooked, he said, and the airline looks to avoid separating families or leaving unaccompanied minors.

A United employee first approached a couple who appeared to be in their mid-20s, Mr. Bridges said, and the pair begrudgingly got off the plane. Then the United employee went to a man five rows behind Mr. Bridges and told him he needed to get off the plane. Mr. Bridges said the man told the employee: “I’m not getting off the plane. I’m a doctor; I have to see patients in the morning.”

Mr. Hobart said: “We explained the scenario to the customer. That customer chose not to get out of his seat.”

The United employee then told the man that if he did not get off the plane, she would call security. As she turned to leave, the man shouted after her, Mr. Bridges said. Specifically, he said, the passenger complained that he had been singled out because he was Chinese.

“It was really intense, really uncomfortable,” he said.

The situation also became uncomfortable for the United employees who then got on board and took the vacated seats, Mr. Bridges said. They were berated by passengers and told they should be ashamed, he said.

The man who had been removed returned to the flight briefly, Mr. Bridges said. Video shows him jogging through the aisle, repeatedly saying, “I have to go home.”

Jayse Anspach, a seminary student who was also on the flight, said that when the man returned to the plane, he ran toward the back. It was not clear how the man had managed to board again.

At one point, the authorities and medics surrounded the man and gave him tissues for his mouth, which was bleeding, Mr. Anspach said. Eventually the man moved to the front of the plane and collapsed sideways into a seat before being taken off the plane on a stretcher, Mr. Anspach said.

The passenger who was forced off the plane immediately called in two lawyers and is suing the company for all injuries. United has confined to giving all passengers on the flight a refund for having to view the incident. United has not confirmed all details to what may happen to the case but they will release later on more details.