A young police officer followed his training when he shot through the window of his patrol car at a suspect who was pointing a gun at him Sunday morning, Baltimore Police Commissioner Kevin Davis said Monday.

Davis said the officer, who is on routine leave, has been with the department for four years, and that the suspect is 21 years old and remains in critical condition in the hospital. Police have not named the officer or the suspect.

Investigators are drawing up charges to file against the suspect, police said.

Police now believe the man wanted to be shot to death — a situation sometimes called "suicide by cop." Davis said that police publicly revealed on Sunday that the suspect's weapon, a 9mm handgun, wasn't loaded in order to reassure officers that someone on the force hadn't been targeted, reports the Baltimore Sun .

"I don't want my police officers in Baltimore to think for one second that this was an ambush with a loaded gun," Davis said. "That's a far different conversation."

Ambushes of officers are rare, but police train to deal with them, and Davis said the young officer handled himself well Sunday.

"I'm just glad that our police officer escaped unharmed," the commissioner said.