The hero boyfriend who died while trying to defend his gal pal from her knife-wielding ex-lover in Brooklyn was accidentally killed by a police bullet, rather than from the stab wounds he suffered in the melee, cops said Wednesday.

Rafael Laureano was inadvertently shot Monday as he desperately attempted to grab a knife from Francisco Carvajal, who was attacking Kataryzna Russo in a jealous rage, according to police.

Carvajal was shot and killed by police, and one stray bullet pierced Laureano’s stomach, cops said.

He later died at a hospital.