Police say in a statement that Josh Collins attacked Angela Cochnauer and James Spurgeon early Saturday. Spurgeon is head of the public safety department of the 1,000-member tribe that's based on a reservation 13 miles south of Yuma.
Authorities say Cochnauer and Spurgeon both had blunt force trauma to the head, and Spurgeon was also stabbed multiple times. They were taken to a local hospital with serious injuries.
The relationship between the trio is unclear.
Police say Collins was found dead from an apparent gunshot wound, which didn't appear to be self-inflicted. No other suspects are being sought.