The gun went off while the officer was cleaning it around 4 p.m. after a practice session at the Circle S Ranch and Shooting Range at 1740 Tomales-Petaluma Road near Two Rock west of Petaluma, Sgt. Debra Barry said.
The bullet broke apart when it hit a concrete table, and fragments of the bullet struck another officer in her face, hand and leg, Barry said.
That officer suffered minor injuries and was taken to Santa Rosa Memorial Hospital, Barry said.
Any further investigation of the incident will be carried out by the Santa Rosa Police Department, Barry said.