Updated

The Latest on a fatal shooting at Oklahoma City's Will Rogers World Airport (all times local):

6:40 a.m.

Flights are operating normally at Oklahoma City's Will Rogers World Airport, where a Southwest Airlines employee was fatally shot Tuesday afternoon.

Airport spokeswoman Karen Carney says air traffic control implemented a ground stop after the shooting of 52-year-old Michael Winchester. The ground stop was lifted at about 6 p.m. Tuesday and flight operations resumed, though 25 flights were canceled because of the incident.

Fifteen of the canceled flights were operated by Southwest Airlines. The company's CEO, Gary Kelly, said on Twitter that the airline "will do everything we can to support Mike's family."

Oklahoma City police have not released the name of the suspected shooter, who was found dead inside a pickup truck from an apparently self-inflicted gunshot wound.

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12:01 a.m.

Oklahoma City police investigators are trying to figure out why a man waited to gun down an airline employee outside Will Rogers World Airport in an ambush that prompted authorities to shut down the state's busiest airport for hours.

Police Capt. Paco Balderrama says the suspected shooter was found dead inside a pickup truck on Tuesday from an apparently self-inflicted gunshot wound. They believe he watched airport employees come and go before shooting and killing 52-year-old Michael Winchester, a Southwest Airlines employee.

Balderrama said late Tuesday that investigators hadn't positively identified the shooter, but that the man apparently knew Winchester's schedule and routine and that the two men likely knew one another.

The 1 p.m. shooting set off a scramble at the airport, with police immediately closing the sprawling complex.