Mr Sime was shot dead after a two hour standoff with police on Sunday night which left an officer and a neighbour injured.
As police today investigated the circumstances in which Mr Sime obtained his firearms licence, Mr O'Connor said the shootout was "clearly" a case of suicide by police.
"We're just lucky...there wasn't a police officer or member of the public killed," he told the Dominion Post.
There were a lot of firearms out there and a lot of people prepared to use them, he said.
It was "naive" for police Commissioner Howard Broad's to say there would never be regularly armed police while he was in charge, Mr O'Connor said.
"How many police officers will it take to be shot at and shot before he reconsiders that? "We have lost three officers this year, this could easily have been four which would have put us at American levels."
Detective Superintendent Brett Kane said Mr Sime had been licensed since 2006 to own sporting shotguns and rifles. He had a criminal history but his last conviction was in 1990 and most of his convictions were for "alcohol-related offending", he told TV One's Close Up last night.
He said police would review how Mr Sime obtained his firearms licence and would talk to the referees who supported his licence application.
"The referees were interviewed and it appears there were no fears or concerns raised in that particular process," Mr Kane said.
Despite reports that neighbours had heard shots from Mr Sime's Burnside property on many occasions, Mr Kane said he was only aware of a neighbour reporting an incident in February this year and police investigated that.
On that occasion they found he was firing his son's bb gun at a cardboard box and no offence was established.
Mr Sime, 42, was shot by an armed offenders squad member after going on a shooting rampage in a quiet cul-de-sac about 8pm Sunday.
He let off more than 80 rounds, peppering neighbouring houses and injuring a police officer and a neighbour.
The officer had minor surgery yesterday to remove pellets from his face and the neighbour was blasted with shotgun pellets from his shoulder to his groin. Both were said to be in a stable condition.
Police said cordons remained in place last night and about 40 residents evacuated from their homes were not likely to be allowed back to their homes for a day or two.
Mr Kane told reporters Mr Sime fired indiscriminately from his wheelchair using a shotgun and a high-powered rifle.
"The number of shots will be confirmed from the investigation, however a neighbour counted at least 82 shots," Mr Kane said.
"Shots were fired from the front and rear of the property and Mr Sime showed some agility. "This was a very dangerous situation. There was extensive damage to a neighbouring house and there is large amount of wadding on the lawn." Mr Sime was a member of the New Zealand Handloaders Association and one of his former clubmates described him as a "reasonable sort of fellow".
Committee member and shotgun convenor Bruce Adams said Mr Sime joined the association about four months ago and would shoot every week on the Christchurch club's shotgun range until the last three weeks.
"He stopped coming. I thought it might have been because of the cold, because it's damn cold out there (on the range) and that might have kept him away," Mr Adams told NZPA.
"He seemed to be a reasonable sort of fellow. But he didn't talk to people much at all. He'd just say gidday and then sit back and not make much conversation.
"We didn't know about his background at all." Mr Sime was not a good marksman because he suffered from muscular dystrophy and was restricted to his wheelchair, Mr Adams said.
"Out of 10 (clay) targets, he might hit four or something like that.
"He used to enjoy himself and was never disappointed (with his shooting), but he never made friends easily."
