A man on a cross-country United Airlines flight violently attacked a sleeping passenger, punching him repeatedly in the face until it was bloody, authorities said. A witness said the man who was attacked is deaf and nonverbal.

Authorities identified the suspect as Everett Chad Nelson, according to an affidavit from an FBI agent.

The incident unfolded Monday on United Flight 2247 about two hours after it took off from San Francisco International Airport for Washington Dulles International Airport in Virginia.

Nelson got up from seat 35F toward the back of the Boeing 737 and went to the lavatory near the front of the plane, according to the affidavit. When he was returning to his seat, he stopped at seat 12F and started punching the man who was sleeping there, according to the affidavit, which didn’t identify the victim.

Sandhya Gupta, who was sitting behind the sleeping man, watched the attack unfold.

“I will not forget the look in his eyes,” Gupta told CBS News. “I had not seen a look from anyone’s eyes like that. It was like he was seeing through the victim.”

According to the FBI affidavit, the attack lasted about a minute. The man screamed as Nelson kept hitting him and his blood was seen on the sleeves of Nelson’s windbreaker, a nearby seat and on the plane’s wall and window, according to the affidavit.

“I actually wondered does this guy have a weapon because I didn’t realize you could do so much damage with just your fists,” Gupta told CBS News. “… His face was bruised and bloody.”

Another passenger rushed up the aisle and wrapped his arms around Nelson to stop him, Gupta said.

“He didn’t fight the person who came to subdue him,” Gupta said. “It was like powering off a robot.”

A doctor on the flight ran toward the man who was attacked and started administering first aid, Gupta said. She said she realized he was deaf and nonverbal when he started signing at the people helping him.

According to the affidavit, the man sustained bruising to his eyes and a gash on his nose. Nelson didn’t appear to be injured, and there wasn’t any indication that the man fought back, according to the affidavit.

Nelson was taken to a seat toward the front of the plane and monitored by the passenger who stopped the attack, according to the affidavit. Gupta said he wasn’t restrained after the attack.

“He just went limp,” Gupta said.

In a statement, United praised the reaction of the passenger and crew.

“Thanks to the quick action of our crew and customers, one passenger was restrained after becoming physically aggressive toward another customer on a flight from San Francisco to Washington Dulles on Monday. The flight landed safely and was met by paramedics and local law enforcement,” the airline said.

Gupta said a flight attendant told her that Nelson claimed the man had attacked him in the street earlier. 

“He kept texting, ‘I’m innocent,'” Gupta said.

The Federal Aviation Administration said in a statement it was investigating the incident. According to the agency, airlines have reported over 1,740 unruly passenger incidents this year and that such incidents have dropped from the record highs reached in early 2021.

Kathryn Krupnik and Ryan Sprouse contributed reporting.