A 73-year-old Texas lawyer is suingUnited Airlinesafter an employeeshoved him to the ground and left him there.

On Tuesday, Houston news station KPRCaired surveillance footage of the 2015 incidentat Houstons Bush Intercontinental Airport.

The video shows passengerRonald Tigner, then 71,talking with a United employee. According to the lawsuit filed last week,Tigner had asked him for helpwith getting a new boarding pass, and the employee laughed and cursed at him.Tigner reportedly toldthe employee to stop smiling, and thats when the employee shoved him. The push is visible in the video.

The video shows Tigner lying on the ground as employees appear to offer no assistance. Not until a fellow passenger rushes over and kneels down beside him does someone call for help.

KPRC also obtaineda 911 call from the incidentin which a United employee says Tigner has fallen down and says he does not know why he fell.

The employee who shoved Tigner was latercharged with injury to an elderly individual, KBRC reports. He was fined and ordered to apologize and attend anger-management classes.

Tigner tried to rectify things with the airline but wasnt pleased with Uniteds slow response, his lawyerWilliam Hoketold HuffPost. Tigner decided to file a lawsuit after seeing footage ofDr. David Dao being dragged off a United flightin April.

[Tigners]main concern was getting his story out there so the traveling public knows about this, and instead of talking about core values [United] will actually do something to stop it, Hoke said. The most astonishing part is that nobody helped him.

United apologized in a statement issued this week.

We have seen the video from 2015 that shows completely unacceptable behavior by a United employee. This employee was terminated from United in August 2015 following the incident. The conduct shown here does not reflect our values or our commitment to treat all of our customers with respect and dignity. We are taking a thorough look into what happened here and reaching out to our customer to profusely apologize for what occurred and to make this right.

United, along withotherairlines, hastaken heatlately for a string of unsavory exchanges between passengers and employees. Besides Dao,a disabled Florida woman sued United, claiming she was injured by employees during a flight from Houston in September. In May, a North Carolina fatherannounced plans to sueUnited after he was accused of molesting his son on a flight.