Lloyd Dean Buie fatally shot Michael Winchester from about 50 yards, firing from the fourth level of a parking garage at his victim, said Capt. Paco Balderrama of the Oklahoma City Police Department.
Buie, 45, was found dead Tuesday in his pickup truck in the five-story garage, with a gunshot wound to his head.
Winchester, 52, was not Buie's immediate supervisor when Buie resigned 19 months ago, Balderrama said.
Buie was an employee from November 1999 until he resigned in April 2015, Southwest said. He was a ramp agent who was suspected of being impaired by alcohol while at work, the airline added. He was asked to take a test to determine his blood alcohol content; he said no and resigned.
Officials haven't disclosed what role Winchester held at Southwest. A since-deleted LinkedIn page described Winchester, a former member of the popular University of Oklahoma Sooners football team, as a ramp supervisor. Southwest said only that he had been with the airline for 29 years.
While retaliation is a possible motive, it is unclear whether Buie targeted Winchester, police said.
"We know his intentions were to go to the airport and hurt someone. We don't know if (Winchester) was his intended target or if he meant to hurt (more people)," Balderrama said.
The shooting prompted an hourslong manhunt that trapped many travelers in the airport terminal, on planes or in their cars. The airport was closed for most of the afternoon and evening Tuesday.
Southwest sent its condolences to the victim's family.
The airline said, "The Southwest Airlines family is deeply saddened by the passing of our Southwest family member, and we extend our heartfelt sympathies and support to his family and Southwest co-workers at this time."
The Winchester name is well-known to fans of the Sooners sports programs. Winchester and his son played football for the team. Mike Winchester was a punter in the mid-1980s and was a member of the 1985 national championship team.
His son, James Winchester
, is a special teams player for the Kansas City Chiefs. On Wednesday, Chiefs head coach Andy Reid addressed the incident, according to CNN affiliate KSHB.
"James is with his family now, where he needs to be," Reid said. "When he comes back, he comes back, but right now it's his time to be with his family. Thoughts and prayers go out to [him] and his family," the coach said.
Mike Winchester's daughters, Carolyn (basketball) and Becca (rowing), also played sports for the university.
"Please keep this beautiful family in your prayers," Sooners athletics director Joe Castiglione tweeted.
Winchester was a good man, James Harryman, the acting undersheriff of the McClain County Sheriff's Office, told CNN affiliate KFOR
"He was a family man, great guy, loved his family, loved his kids, grandkids, was always there for them and with them at ball games," Harryman said.
Five airlines fly out of Will Rogers to 21 destinations. The airport sees 150 commercial flights a day and more than 3.6 million passengers each year, the city's website says. At least 25 flights were canceled Tuesday, Will Rogers World Airport spokesperson Karen Carney said.
was waiting for his flight to Dallas when the airport went on lockdown. He told CNN that most people were calm. "There is that air of wanting to get going, " he said. "Most of us will miss our connections to wherever we are heading."
The airport said on its website
that it operated a normal schedule Wednesday, but advised passengers to arrive 90 minutes before departing flights.