A man who shot a Southwest Airlines employee outside Oklahoma City's airport likely did so in retaliation for having lost his own job with the airline last year, police said.
Lloyd Dean Buie, 45, killed Michael Winchester on Tuesday as the 52-year-old was leaving work and walking to an employee car park, Police Captain Paco Balderrama said at a news conference.
Buie fired the shot from the fourth floor of a car park when Winchester was about 50 metres away, he said.
The shooter was later found dead in his pick-up truck in the car park, and police think he shot himself.
"We know his intention was to go to the airport to hurt someone," Balderrama said. "The suspect knew where the employees parked and where they would be walking."
Buie quit his job as a ramp agent for Southwest Airlines in April 2015 after he refused to take an alcohol screening, airline spokeswoman Brandy King said.
She said co-workers had suspected Buie was under the influence at work, but she declined to say whether Winchester, a ramp supervisor who had worked for Southwest for 29 years, was involved or to describe any interactions the two men may have had.
"Our Southwest family is grieving, as we are deeply saddened by the loss of our family member.
"Our focus remains on offering support to the Winchester family and Southwest employees during this difficult time," King said.
Police said Winchester was not Buie's immediate supervisor, but they believe the incident that led to Buie's resignation likely served as motive for the attack.
Winchester has a listed address in Washington, a community about 35 miles south of the airport.
The shooting set off a scramble at Will Rogers World Airport, with police immediately closing the sprawling complex and asking passengers to seek cover.
They diverted incoming flights and refused to give already-loaded aircraft permission to leave.
There were concerns the gunman might have entered the terminal and mingled among passengers or employees.
Police found Buie's pick-up truck about three hours after the shooting. They used a robot to determine he was dead inside it before giving the all-clear.
Balderrama said Buie likely would have needed a scope on his rifle to shoot Winchester from that distance.
"It would definitely require familiarity with a rifle," he said. "You don't have to be an expert marksman to hit a 50-yard shot, but it's not an easy shot either."
The attack led to the cancellation of 25 flights. Normal airport operations resumed on Wednesday.
The airport handles between 7,000 and 8,000 passengers daily for Alaska, Delta, Southwest and United airlines and has a separate terminal that serves as a transfer centre for federal inmates.