FRESNO, Calif. (AP) — Police in California say a police detective fatally shot a man who was attacking him inside his office Tuesday at police headquarters.

The man was not supposed to be at the police department’s headquarters and it was not immediately clear how he gained access to the building, which has secured gates and doors, said Fresno Police Chief Paco Balderrama.

“It’s very troubling to me to figure out that a person with bad intentions could enter into police headquarters and cause harm to one of my police officers,” Balderrama said during a news conference.

He said the man entered the detective’s office on the first floor and began assaulting him with an unknown object, cutting the officer on the neck and head. After a struggle, the officer fired at least one shot, killing the man, Balderrama said.

He didn’t identify the man but described him as 6 feet (1.8 meters) tall, more than 300 pounds (136 kilograms) and around 25 years old.

The officer, who is in his late 40s or early 50s, was taken to a hospital and is expected to recover, Balderrama said.

Balderrama said police are still trying to determine the reason for the attack and whether the man used a knife or an object he found at the detective’s office.

“We don’t know what their motive is at this point. What we do know is that these last couple of years, we’ve seen an increase in assaults on police officers across the country,” Balderrama said. “I don’t want to speculate as to what the motive was, what the intentions were of this individual but I am very glad to say that my officer is going to be okay.”

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