(CNN) -- An attorney for David Dao, the passenger forcefully removed from a United Airlines flight earlier this week, outlined the 69-year-old physician's injuries and told reporters Thursday he would file a lawsuit once they had completed their due diligence.
Already, the legal team has filed a chancery motion asking that all evidence in the case be preserved.
Dao suffered "a significant concussion as a result of disembarking that plane," attorney Thomas Demetrio said in a news conference in Chicago. Dao also lost two front teeth, has a broken nose and incurred injuries to his sinuses, and will be "undergoing reconstructive surgery in that regard," Demetrio said.
As millions saw via traditional and social media, Dao was aboard a Louisville, Kentucky-bound flight out of Chicago on Sunday night when Chicago aviation security officers forcefully pulled him from his seat and dragged him down the aisle of United Airlines Flight 3411.
His fellow passengers looked on, many of them filming it the incident. United would say later it had to remove Dao to make room for four of its own dead-heading employees, who needed to get to Louisville.
The airline offered compensation at first, but when that didn't convince enough passengers to take a later flight, it picked Dao randomly. In video shot by Joya and Forest Cummings, who were sitting behind him, Dao repeatedly refuses to disembark, explaining he is a physician and must work in the morning.
Passenger Jayse Anspach told CNN that Dao and his wife initially agreed to take a later flight, but recanted upon learning that that flight wouldn't take off till Monday morning.
"He was very emphatic: 'I can't be late. I'm a doctor. I've got to be there tomorrow,'" Anspach recalled.
The Cummingses said Dao was not belligerent and got only mildly upset when a second security officer arrived, demanding he leave the plane, they said. Dao never raised his voice, the couple said.
As security officers pry Dao from his seat, he screams. In video shot after the altercation, streaks of dry blood run from the Kentucky doctor's mouth. Passengers said he hit his head on an armrest.
Asked later what was injured, Dao said "everything," CNN affiliate WLKY reported. He was discharged from the hospital late Wednesday night, Demetrio said.
Three Chicago Department of Aviation officers are on leave following the incident, and the airline's stock plummeted amid boycott threats. The company has since offered refunds to all passengers on that flight.
United Airlines CEO Oscar Munoz initially claimed Dao was belligerent, leaving security officers no choice but to employ force in removing him.
Munoz later struck a tone of contrition, telling ABC's "Good Morning America" Wednesday that he felt "ashamed" over the incident and vowed never again to let law enforcement remove "a booked, paid, seated passenger" from a plane.
As for Munoz's earlier claim that Dao was at fault due to his belligerence, the CEO changed his heading, telling the morning show, "He can't be. He was a paying passenger sitting on our seat in our aircraft, and no one should be treated like that. Period."
The incident repulsed many United customers, some protesting by cutting up their United mileage cards.
"My new #united card. Not planning to fly them any more after this," Josh Perfetto tweeted.
United took a hit on the stock market. Shares in United Airlines slipped by 4% Tuesday, and the company's market value plummeted by $1 billion.
Anyone can be kicked off an overbooked flight against their will. It's an oft-overlooked policy to which passengers agree when they book tickets. Overbooking is legal, and most airlines do it in anticipation of no-shows, the US Department of Transportation said.
In 2015 alone, 46,000 customers were involuntarily bumped from flights, according to the Department of Transportation.