OAKLAND, Calif. (AP) — An Oakland police officer was shot and killed Friday while answering a report of a burglary at a marijuana dispensary, authorities said.

The officer was one of several who responded to a report of a burglary in progress at the cannabis business near Jack London Square at about 4:30 a.m., about 3 1/2 hours after an earlier burglary was reported at the same business, authorities said.

The arriving uniformed and plainclothes officers saw several people leaving the business and one opened fire several times, hitting the officer, who was in plainclothes and driving an unmarked car, interim Police Chief Darren Allison said at a news conference.

Other officers took the wounded officer to a hospital, where he was pronounced dead about four hours after the shooting. His name wasn’t immediately released but he had been with the department for four years, Allison said.

No officers returned fire, the chief said.

No arrests were immediately made, but Allison said investigators were following up on a lot of “actionable” evidence. He didn’t provide details.

“The dangers and demands of this profession are real, and come with significant sacrifice,” the chief said. “Sadly, today, one of our officers paid the ultimate sacrifice.”

Mayor Sheng Thao called the killing a senseless act of violence and said she was devastated by the officer’s death.

“I know the entire Oakland community feels the profound impact of this loss,” she said in a statement.

“I am proud of the officers who responded this morning and carried their brother to the hospital on their shoulders,” Barry Donelan, president of the Oakland Police Officers’ Association, said in a statement. “Their actions personified what it means to be an Oakland police officer. As we mourn, rest assured that we are also determined to bring this cop killer to justice.”

It was the 54th death of an Oakland officer in the line of duty, coming amid a robbery-driven rise in violent crime. Robberies where a gun was used increased 37% this year over the same period last year, according to Police Department figures cited by the San Francisco Chronicle.