A post-mortem shows Napier gunman Jan Molenaar died from a gunshot wound to the head.
Molenaar's body was found on Saturday after a 50-hour siege during which he fatally shot Senior Constable Len Snee, 53, at his Chaucer Rd property.
Two other officers and a civilian were seriously wounded.
A memo issued by the Coroner says all evidence points to 51-year-old Molenaar's head wound being self-inflicted and he had no injuries caused by police.
That means two shots fired by police did not hit Molenaar.
Detective Superintendent Rod Drew says there is evidence to support 21 cases of attempted murder, as well as the murder of Senior Constable Snee.
Mr Drew said police found an arsenal of fully loaded guns and ready to be fired in Molenaar's bedroom. The gunman was found wearing protective clothing.