The victim, PO1 Joel Cosme, died from gunshot wounds in the chest, said Chief Inspector Salvador Caro, Mabini police chief.
The suspect, PO1 Nelson Mariano, whom Cosme managed to shoot in the armpit, tried to escape but was arrested by pursuing lawmen when his vehicle crashed into a lamppost in Barangay Balibaguhan.
Both were assigned to Camp Crames administration holding center and the Philippine Drug Enforcement Agencwys NCR office.
Caro said Cosme tried to stop Mariano, who was already drunk, from firing his 9-mm pistol during the birthday party they attended in Barangay Sto. Tomas, Mabini town.
A verbal tussle ensued, and moments later, Mariano shot Cosme in the chest. Though wounded, Cosme managed to shoot back, hitting Mariano in the armpit. Ed Amoroso, Arnell Ozaeta and Cecille Suerte Felipe