Phnom Penh police said the incident happened at around 1:25 p.m. on Street 360, Sangkat Boeung Keng Kang 3, Khan Boeung Keng Kang, the Khmer Times reported.
The Vietnamese victim, whose identity has not been verified, was about 30 years old. Their body has been taken to the Stung Meanchey Pagoda, waiting for relatives to come.
The police had arrested the man who allegedly shot the Vietnamese.
Sources said the gunman and the victim were seen arguing with each other.