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FREDERICK, Md. — A Navy medic shot and critically wounded two U.S. Navy sailors at a Maryland business park Tuesday, then fled to a nearby Army base where he was shot and killed, police and U.S. Navy officials said.

Fantahun Girma Woldesenbet, a petty officer third class assigned to Fort Detrick, began shooting with a rifle inside a Navy-related business at the Riverside Tech Park, causing people inside to flee, Frederick police and Fort Detrick officials said at a news conference. Frederick Police Chief Jason Lando said detectives are still trying to determine a possible motive.

Brigadier General Michael J. Talley said Woldesenbet drove to the base after the initial shooting at the office park and sped past the gate before he could be searched. Talley said he made it about a half-mile into the installation before he was stopped at a parking lot. He then brandished his weapon at officers from the installation’s police force who had pursued him.

Talley said investigators are looking at whether the shooter knew the victims, but refused to speculate, saying, “We don’t want to compromise any aspect of the investigation.”

Fort Detrick is home to the military’s flagship biological defense laboratory and several federal civilian biodefense labs. About 10,000 military personnel and civilians work on the base, which encompasses about 1,300 acres (526 hectares) in the city of Frederick.

The base is a huge economic driver in the region, drawing scientists, military personnel and their families. Frederick Mayor Michael O’Connor noted that various defense contractors are located near Fort Detrick and that it wouldn’t be unusual for a member of the military to be off base and working with a private firm that does business with the U.S. government.

“When these incidents happen in other places, you’re always grateful that it’s not your community,” O’Connor added. “But you always know, perhaps in the back of your mind, that that’s just luck — that there isn’t any reason why it couldn’t happen here. And today it did.”

By early afternoon, the Nallin Farm gate at Fort Detrick through which the shooter entered remained closed and two officers were standing by.

Mark Nelson, a firefighter who lives in a row of townhomes across the street from the base, said he heard the base blast warning sirens Tuesday morning.

“I heard, I don’t know what they call it, but they were like air raid sirens, and I knew something was going on,” Nelson said.

Lando called the shootings “very tragic.”

“It’s happening too frequently,” he said. Every time we turn on the TV we’re seeing something like this happening. And now it’s happening in our backyards.”