The shooting occurred on Saturday night in Srey Prey Village, when officer Oum Vuthy opened fire on the family, Cambodian media reported. Authorities later issued a wanted notice, offered a US$1,000 reward for information leading to his capture, and urged him to surrender.
Kampot provincial police said Monday that Vuthy had been arrested. He faces charges of murder and illegal possession of a weapon, according to Khmer Times.
The dispute reportedly began when a black dog ran into a gathering where family members were grilling meat, snatched a piece of fish and ran off.
A relative threw a sandal to chase the dog but accidentally struck Vuthy's wife, sparking an argument.
She then called her husband, who allegedly arrived by motorbike and fired about 20 shots with an unspecified firearm, causing the deaths and injuries.
Police have also arrested Vuthy's wife for her alleged involvement, Kiri Post reported.