CHICAGO - The CEO of United Airlines has issued a stronger apology about a passenger who was dragged off a United Express flight, calling the confrontation "truly horrific."

Oscar Munoz said in a note to employees Tuesday that he continues to be disturbed by the events Sunday night in Chicago.

He said, "No one should ever be mistreated this way."

Munoz was widely criticized for two statements Monday about the altercation in which he described the 69-year-old man taken off the plane as "disruptive and belligerent."

On Tuesday, Munoz said he was committed to "fix what's broken so this never happens again." He pledged to review the company's policies for seeking volunteers to give up their seats, for handling oversold flights and for partnering with airport authorities and local law enforcement.

The company plans to share results of the review by April 30.

It was also revealed that the man dragged from the flight is a Kentucky physician was convicted more than a decade ago of felony charges involving his prescribing of drugs.

The passenger's unflattering history quickly became the focus of attention, even though there's no indication that his past influenced how he was treated or that the airline or airport police were aware of his background.

A person with knowledge of the flight who was not authorized to publicly release the information told The Associated Press that the passenger was David Dao, 69, of Elizabethtown, Kentucky.

Dao has not returned messages from the AP. He was captured on cellphone video getting removed from a flight Sunday at Chicago's O'Hare Airport.

According to state of Kentucky documents, Dao was investigated for fraudulently prescribing drugs to a person with whom he was involved sexually. He was convicted of felony counts of obtaining drugs by fraud and deceit. His license was restored in 2015.