"One individual assaulted," according to Broadcastify audio.
The FBI says suspect Everett Chad Nelson was walking back to his seat from the bathroom when he attacked a person sleeping in a random row.
"The next thing I know, I just hear the this blood curdling screams," said witness Sandhya Gupta.
The victim as a deaf man.
"When he was trying to communicate with us in sign language that's when we realized he was deaf," said Gupta.
PREVIOUS STORY: Deaf man 'viciously' attacked while sleeping on United flight out of SFO: passenger
Deaf man attacked on United flight out of SFO
"Airlines are not required to have sign language interpreters on their flights. There's no way. First of all, there's not that many sign language interpreters in the world," said Jan Garrett, Deputy Director for the Pacific ADA Center.
"Under the Air Carrier Access Act, there are some requirements about trying to provide, you know, as effective communication as you can whether that's writing notes or whatever it is, texting, whatever it is," Garrett said.
The witness described the victim as doing exactly that, texting with the flight crew.
"He also just kept texting, 'I'm so scared.' Like it was just awful, Gupta said.
United Airlines released a statement, writing in part:
"Thanks to the quick action of our crew and customers, one passenger was restrained after becoming physically aggressive toward another customer. The flight landed safely and was met by paramedics and local law enforcement."
MORE: Fight breaks out mid-air on Southwest flight from Oakland to Kauai
And that's where the experts say a Complaint Resolution Official - or CRO- comes into play.
"Once they got to the destination airport, they should have been able to have the CRO work with the passenger to get whatever interpreter or communication was needed because there's supposed to be CRO for every airline, every airport, 24/7," said Garrett.
ABC7 reached out to United Thursday night for more about their process and are waiting to hear back.
In the meantime, the suspect is still in jail after being arrested shortly after the flight landed at Dulles.