District Voluntary Force (DVF) constable Narendra Khandapan killed his father-in-law, mother-in-law, brother-in-law and two other relatives at his rented house in Koraput, about 500 km from here.
Khandapan committed suicide by shooting himself after killing his relatives, Inspector General of Police (south-western range) Yashwant Jethwa told IANS.
"All the deceased have gunshot injuries. Motive appears to be a family dispute," he said.
The DVF is part of Odisha police. It plays a key role in anti-Maoist operations in the state.