Officers with Fontana Police Department responded to a reported domestic dispute at an apartment in the 9100 block of Date Avenue.
As the apartment door was opened, police say a man pointed a gun at them, and the officers opened fire.
The man was transported to the hospital, where he was pronounced dead. Police said a firearm was recovered at the scene.
No officers were injured.
The San Bernardino County Sheriff's Department is investigating the incident. Fontana PD will also conduct an internal administrative review.