Edward Hamilton Livingstone (51), the estranged husband of Katharine Webb, was the subject of a protection order to not associate with her, and last year was twice charged with breaching the order.
Ms Webb went to neighbours for help after Livingstone turned up at the Kiwi St home in St Leonards armed with a gun, which was later used to kill his children before he turned it on himself.
Until a week before the shootings, Livingstone had been living in Milton and worked in administration at the Otago Corrections Facility at Milburn.
The Otago Daily Times understands the murder weapon was taken from his former flatmate's gun safe by Livingstone after he accessed a key.
That allegation was put to Inspector Greg Sparrow, area commander Dunedin Clutha Waitaki, who responded with a statement:''Police identified early on in their inquiries how Livingstone accessed the gun and these details form part of our inquiries and investigation.
''The aspects you have raised form a significant part of our investigations, as do those that specifically relate to Edward Livingstone and his circumstances.''
Last week police confirmed Livingstone did not have a firearms licence. Mr Livingstone's former flatmate could not be reached for comment yesterday.
University of Otago National Centre for Peace and Conflict Studies director Kevin Clements said for a protection order to work effectively it was important the offender had no access to firearms.
He expected police would check any address to ascertain the availability of firearms.
Previously, New Zealand registered firearms as opposed to firearms owners, ''and the problem is you don't know how many guns, unless they are handguns or semi-automatics, are at each house.
''That means police and nobody else knows how many guns licensed gun owners have.''
If Livingstone was able to source the murder weapon from a person he had been living with, then ''there is a major deficiency in the process''.
New Zealand had about 230,000 licensed firearms owners and an estimated 1.2 million firearms, he said.
Of those, an estimated 25,000 firearms were in criminal hands, and 45,000 were owned by the Defence Force.
