The handgun the Rev. Joseph F. Moreno Jr. used to kill himself was once owned by a Kenmore-Town of Tonawanda resident some 40 years ago, authorities said Friday.

Investigators are trying to determine if the former owner is still alive. If so, he would be 99 years old.

“We’re checking to see if there are any forms that would show the gun was sold or given to someone else,” a police source said.

Members of the federal Bureau of Alcohol, Tobacco, Firearms and Explosives are assisting city police in the investigation, which is concentrated on trying to establish how the .38-caliber handgun ended up with Moreno. His body was found Oct. 13 in the rectory at St. Lawrence Catholic Church on East Delavan Avenue, where he had served as pastoral administrator.

The gun was found next to the 54-year-old priest’s body, police said.

Scenarios being considered by authorities are that the gun had been stolen from the original owner, or the owner died and it ended up in the hands of someone close to him who then might have later passed it along to the priest.

One individual familiar with the investigation said it was possible the weapon had been given to Moreno for protection. He had reported to police in 2006 that he fought off a would-be burglar in a violent confrontation at the East Side parish.

However, authorities never solved that case and later said it was doubtful the incident ever occurred.