The man suspected of fatally shooting the father of an NFL player outside of Oklahoma City's main airport terminal was identified Wednesday morning as one of his ex-co-workers at Southwest Airlines.

Police said the gunman, 45-year-old Lloyd Buie, may have held a grudge against his former colleague and workplace when he opened fire Tuesday afternoon at the Will Rogers World Airport. Buie was fired from the airport's Southwest Airlines branch in April 2015, Oklahoma City police said at a news conference.

Buie's victim — 52-year-old Michael Winchester — was also an employee at Southwest Airlines, officials said. He was not Buie's immediate supervisor.

Related: Father of NFL Player Gunned Down at Oklahoma City Airport

Buie was found dead in his pickup truck at the airport with a self-inflicted gunshot wound to the head, police said. His exact position with Southwest and the reason for his termination was not immediately known.

"We know his intentions were to go to the airport to hurt someone, and he did," Oklahoma City police Capt. Paco Balderrama told reporters. "We don’t know if [Winchester] was the intended target."

Authorities are continuing to determine a motive for why Buie killed Winchester, who was also the father of James Winchester, a long snapper for the Kansas City Chiefs.

Buie was positioned on an upper floor of a parking deck about 50 yards away from Winchester when he opened fire with a rifle at around 1 p.m. local time, Balderrama said. Winchester, himself a former University of Oklahoma football player, had just left work and was walking toward his car.

It's unclear whether Buie planned to target other former co-workers.

The shooting set off a scramble at the airport, with police immediately closing the sprawling complex and asking passengers inside to seek cover.

Balderrama initially said police had received reports of a possible second victim, but no one was found.

Flights were operating normally Wednesday at Will Rogers World Airport.