 Lon Nol saw Cambodia 's population of 400 @,@ 000 ethnic Vietnamese as possible hostages to prevent PAVN attacks and ordered their <unk> and <unk> . Cambodian soldiers and civilians then unleashed a reign of terror , murdering thousands of Vietnamese civilians . On 15 April for example , 800 Vietnamese men had been rounded up at the village of <unk> <unk> , tied together , executed , and their bodies dumped into the Mekong River . They then floated downstream into South Vietnam . Cambodia 's actions were denounced by both the North and South Vietnamese governments . 
