Napier gunman Jan Molenaar was in possession of two rifles that he bought from the Defence Force.
Molenaar shot three police officers, killing Senior Constable Len Snee, after his home was searched by police executing a search warrant in May.
Molenaar remained holed up in his Hospital Hill home with the automatic rifles for more than 24 hours before committing suicide.
The rifles Molenaar used were standard issue to Defence Force personnel between the 1960s and 1980s.
Molenaar did not possess a firearms licence at the time of the shootings in May.
Defence Force spokesman Commander Shaun Fogarty said the guns were made obsolete by the introduction of the Steyr rifle.
"Obsolete weapons were sold-off in accordance with regulations of the time, and could be bought by members of the New Zealand public," Mr Fogarty said.
However, the Defence Force could not say just how many weapons had been sold to the public. A spokesman said he would try to find out but has so far not returned phone calls.
Mr Fogarty said since 1999, only one 9mm pistol has been reported missing and the military is now installing microchips into its guns.
Before that however, records show that between 1990 and 1997, six 9mm pistols and two Steyr rifles were reported as missing or not accounted for.
Decommissioned weapons that have been made unusable are also missing including a grenade launcher, sub-machine gun, and two rifles.
"As the Napier incident proves, weapons that end up in the hands of the wrong people can have terrible consequences, said Mr Fogarty.
The Defence Force has also revealed that the cost of sending the two light armoured vehicles to Napier was $5715. That figure includes meals, accommodation, allowances, road user charges and fuel but not routine maintenance.
- NZ HERALD STAFF
Napier gunman had ex-Defence Force rifles in his possession
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