Butler, 53, was found dead at a Wikitoria Rd property on April 22.
Another man in his 50s was found seriously injured at the property and taken to Whanganui Hospital.
The police dive squad searched the Whanganui River a few days after Butler's death in the hope of finding discarded weapons.
Police earlier said Butler's death was not the result of a random attack and the people involved in the incident were known to each other.
After an Official Information Act request by NZME, Corrections confirmed on Tuesday that Butler had been on a community-based sentence.
It is believed Butler had been on home detention.