The shooting took place this weekend in the village of Akoko in Nigeria's Delta state. Delta state police spokesman Charles Muka said Monday that the officers opened fire for no reason after drinking heavily.
Muka said the four officers were being held pending the filing of criminal charges over the shooting.
Nigeria's federal police remain incapable of stopping ethnic and religious violence sweeping the oil-rich nation. Critics say its officers instead shake down motorists for bribes and make sham arrests to demand bail money from families. Many officers serve as personal orderlies to the country's elite.