A California detective fatally shot a man who attacked him after breaking into the headquarters of the Fresno Police Department on Tuesday morning, officials said.

The hulking suspect breached the secure facility at about 11:45 a.m. and entered the detective’s office, where he began hitting the cop with an unknown object and slashing him with a knife in the forehead and neck, Fresno Police Chief Paco Balderrama said in a Facebook Live update.

The 25-year veteran of the department, who was much smaller than the 300-pound intruder, managed to pull out his police-issued firearm and shoot the suspect at least once, according to police.

The suspect was pronounced dead at the scene and the detective was being treated in the hospital, where he was expected to recover, Balderrama said.

“From what we know right now this person should not have been here,” the chief told reporters. “He did not have an appointment with anyone.”

“We don’t know what the motive is at this point. What we do know is that this last couple of years we have seen an increase of assaults on police officers across the country,” Balderrama added.

Police were reviewing security footage to investigate how the suspect was able to gain access to the gated building, which has multiple layers of electronic security checkpoints, officials said.