Updated

Two people who were in a car with a U.S. airman when he drove to a North Dakota Wal-Mart and opened fire inside the store had no idea what he was going to do, police said Wednesday.

Grand Forks Police Lt. Derik Zimmel said Marcell Willis, 21, made up a reason to go to Wal-Mart around 1 a.m. Tuesday. The two people with him stayed inside the car while he went into the store, where he killed one worker and injured another near the self-checkout area in front of the store, then killed himself.

Police have yet to find a motive behind the shooting. Zimmel said the people who were with Willis also do not seem to know why he did it.

"To the best as we can tell at this point, they were as clueless as to his motives as anybody else," Zimmel said.

Zimmel did not reveal what ties the passengers had to Willis. He said authorities were treating them as witnesses, not suspects.

Police have identified the victims as Gregory Weiland, 70, of Grand Forks, who was killed, and Lis Braun, 47, also of Grand Forks, who was injured. Zimmel said authorities were not releasing the name of the third worker whom Willis shot at but missed.

An autopsy will determine whether Willis had drugs or alcohol in his system. Police did not say when the results would be made available.

Willis had been stationed at Grand Forks Air Force Base, about a dozen miles west of the city, since February 2013 and had achieved the rank of senior airman, the base said.

Sgt. David Dobrydney, a spokesman for the base, said he could not release any information on Willis’ service record “due to the possible impact on the ongoing investigation.”

Willis’ father, Sean Willis, told The Associated Press Tuesday that his son had been in the military for about three years and was originally from Springfield, Tennessee.

Weiland, an overnight cashier, and Braun, the overnight grocery general manager, were near one another in the self-checkout area at the time of the shooting, Wal-Mart spokesman Brian Nick said.

Weiland had worked for the company for 24 years, though it was not clear whether all of those were spent at the Grand Forks store. Braun has worked at the store since September 2009.

Austin Owens, 25, said his family and Weiland's family were longtime neighbors in rural Warren, Minnesota. Owens said Weiland helped jumpstart his farming career by giving him "a generous deal" on a land sale and continued to help with advice and encouragement.

"He was always very cheerful," Owens said. "Even if it was raining, he took the positives out of everything."

He said Weiland enjoyed working at Wal-Mart.

"He said he loved the company of the employees and he loved his job and he didn't mind having a little cash on hand from his paycheck," Owens said.

Larry Friesz, Braun’s 70-year-old father, said his daughter told him she expects to be hospitalized for up to four days. Friesz said he’s been busy farming and had not had a chance to visit his daughter, but they spoke briefly on the phone.

Friesz said he was shocked by what happened.

"You always read about it," he said of such violent incidents. "But when it's your own kid, it's different."

Braun is in satisfactory condition, Altru Hospital spokeswoman Angie Laxdal said Wednesday.

About 1,500 airmen are assigned to Grand Forks Air Force Base, which was home to air refueling tankers for 50 years until a round of military base closings and realignments took that away. The last tankers left in 2011 and the base has taken on an unmanned aircraft mission.

The Associated Press contributed to this report.