Police say the officers on scene feared for their lives and fired. The victim was rushed to the hospital, where he later died.
Family members identify the man killed as 42-year-old Rocketi Seu.
"Police asked him to get down. He didn't listen, mentally ill, and they tasered him. He went down. After that, they assumed kicking him," said Uli Toomalatai, nephew of the victim.
Police say after the shooting, some 40 people gathered, making the officers feel that their safety was in jeopardy, so more units were called in.
Family members of the man killed say he was unarmed, and police didn't need to use deadly force.