Napier gunman Jan Molenaar was determined to go down fighting rather than face jail, according to police.
Investigations are continuing into the murder of Senior Constable Len Snee by the 51-year-old gunman on 7 May.
The officer and two others were carrying out a routine drug raid when they were shot at Molenaar.
The surviving officers and a civilian man suffered serious injuries during the incident.
The gunman's body was found in his Chaucer Rd home at the end of a two-day siege.
Detective Superintendent Rod Drew says a picture of what led to the shootout is complete.
Mr Drew says Molenaar had been growing and dealing cannabis for more than 10 years, but was unable to accept the possibility of going to jail or the confiscation of his house.
Police say no-one will be charged in relation to the attack on 7 May.