A policeman was found shot in the head and back in a police box in Hikone, Shiga Prefecture, western Japan, Wednesday evening.
Sergeant Akira Imoto, 41, was sent to a hospital and confirmed dead. The Shiga prefectural police suspect his colleague, Tomohiro Onishi, 19, shot the victim and ran away.
Onishi was held in the small hours of Thursday.
Police received an emergency call around 8:15 p.m. (11:15 a.m. GMT) saying that a police car was found shoved into a rice paddy in Aisho near Hikone.
As nobody was found in the car, Hikone police station staff visited the police box, to which the car belongs. The staff found bleeding Imoto slumping over a desk around 8:45 p.m.