The 69-year-old man dragged from a United Airlines flight in a bloody scuffle — igniting outrage over his treatment — has been identified as a Kentucky physician as the airline's CEO issued another apology and ordered a "thorough review."

While United Airlines CEO Oscar Munoz apologized in a public statement Monday and said the airline is investigating, he also accused Dr. David Dao of being "disruptive and belligerent" in an internal letter seen by NBC News. The mounting criticism led Munoz to tell United employees Tuesday that the embattled company would work "to make it right" amid its public relations tailspin.

"Like you, I continue to be disturbed by what happened on this flight and I deeply apologize to the customer forcibly removed and to all the customers aboard," Munoz said.

"I have committed to our customers and our employees that we are going to fix what’s broken so this never happens again. This will include a thorough review of crew movement, our policies for incentivizing volunteers in these situations, how we handle oversold situations and an examination of how we partner with airport authorities and local law enforcement," Munoz said, adding that the results would be available by April 30.

Dao is seen on cellphone video that captures the chaos aboard Sunday's United Express Flight 3411 from Chicago to Louisville, two aviation sources confirmed to NBC News on Tuesday. Dao was one of four people randomly selected to get off the oversold plane just before takeoff because extra crew needed the seats.

An attorney for Dao’s family said in a statement to CNBC Tuesday that his family is grateful for the support and is asking for privacy at this time.

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"The family of Dr. Dao wants the world to know that they are very appreciative of the outpouring of prayers, concern and support they have received. Currently, they are focused only on Dr. Dao’s medical care and treatment,” Chicago attorney Stephen L. Golan, one of two lawyers representing the family.

"Until Dr. Dao is released from the hospital, the family is asking for privacy and will not be making any statements to the media," the attorneys said in the statement.

Eyewitnesses on the flight said Dao had referred to himself as a doctor, and didn't want to leave the plane because he needed to get home and see patients the following day. He was yanked out of his seat and fell, hitting his head on an armrest and causing it to bleed, Chicago police said.

The men removing him were unarmed security officers with the Chicago Department of Aviation.

Once taken off the plane, Dao managed to board again, passenger Tyler Bridges told NBC News: "He runs back on — dazed, bloodied, kind of in a mess — yelling, 'I have to get home, I have to get home.'"

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Another passenger, Joya Cummings, said that she and her son were sitting in the row directly behind Dao, and that originally, the doctor and his wife volunteered to take an $800 voucher for willingly giving up their seats.

But once they realized there were no other flights that night, the couple declined, Cummings said. When the airline failed to find volunteers, the crew said they would choose people randomly — and that's when Dao was selected.

Throughout the encounter, Cummings said, Dao was upset but not belligerent or violent. Once officers were called on board, she added, Dao was "calm and soft-spoken" and didn't act violently with officers.

"Other than not getting out of the seat, he didn’t fight back. He just stood his ground,” Cummings said.

The incident surrounding Dao has prompted questions about passengers' rights and led some members of Congress to demand an investigation. Social media users in Vietnam and China have also grown incensed over his treatment, claiming he was targeted for removal from the flight because of his race.

Airlines routinely ask passengers to give up their seats on overbooked flights in exchange for travel vouchers, and federal rules require a carrier to first ask for volunteers before forcing anyone off.