A retired police sergeant who was questioned after a possible mob slaying has been killed by NYPD officers during a gun battle.

The incident occurred as police responded to a domestic dispute at Jason Aiello's Staten Island home around 6:40 a.m. Tuesday.

They say Aiello fired first — seven times total. He was hit three times by police, who fired a total of 19 rounds. Police say their shooting appears justified.

Authorities say Aiello was the bodyguard of a prominent jeweler gunned down outside a Staten Island restaurant in April. Federal and city prosecutors say Aiello was driving at the time of the slaying and had been recently questioned.

Federal and city officials are looking into whether the jeweler had business dealings with members of the Genovese crime family.