A Navy medic shot and wounded two U.S. sailors at a military facility Tuesday, then fled to a nearby Army base where security forces shot and killed him, police and Navy officials said.

Authorities said they had yet to determine what drove 38-year-old Fantahun Girma Woldesenbet to open fire at the facility, located in an office park in Frederick, Maryland.

“We’re still trying to sort through stacks of paper … to figure out exactly what the motive would be,” said Frederick Police Lt. Andrew Alcorn.

Woldesenbet shot the sailors with a rifle inside the facility at the Riverside Tech Park on Tuesday morning, causing people inside to flee, said Frederick Police Chief Jason Lando.

Woldesenbet, a Navy medic assigned to Fort Detrick but who lived in town, then drove to the base, where gate guards who had been given advance notice told him to pull over for a search, said Brig. Gen. Michael J. Talley. But Woldesenbet immediately sped off, making it about a half-mile into the installation before he was stopped at a parking lot by the base’s police force. When he pulled out a weapon, the police shot and killed him, Talley said.

The two sailors, who Talley said were assigned to Fort Detrick, were airlifted to a hospital. Police said one victim is in critical but stable condition, and the other is in serious condition but expected to be released Wednesday.

Talley said investigators will determine as much as they can, including why the suspect went back to the base.