A Beretta 9 mm semi-automatic handgun that was stolen from a family member was used by Clayborne Conley in the fatal shooting a Makiki woman and her teenage daughter before he turned it on himself, police said.

Police said the gun had been reported stolen on the day of the shootings, but would not name the gun’s owner.

Police said Conley broke into Kristine Cass’s home early in the morning of Aug. 20, killed Cass and her 13-year-old daughter, Saundra, then committed suicide.

Conley, a former Hawaii National Guardsman, and Cass had dated off and on, but she had recently called off the relationship, according to friends.

Cass told a friend that she had decided to get a temporary restraining order against Conley after their relationship took a turn for the worse.

Because Conley had previously been acquitted of a crime on the grounds of mental illness, state law barred him from owning and registering a gun.

The 9 mm handgun registered to one of Conley’s family members is the standard-issue sidearm for the U.S. Army and is also used commonly by law enforcement agencies, although not Honolulu police.

In 2009, there were 22,856 firearms registered on Oahu, police spokeswoman Michelle Yu said. The total includes handguns and rifles.

But Yu stressed that the number isn’t a true reflection of how many registered guns circulate on the island.

"After a firearm is registered, there’s no way to know if a firearm is sold or transferred out of state," she said. "It’s difficult to know how many firearms are out there; the documents go back to 1927 when we were still a territory."