BUSHWICK (WABC) -- An elderly Brooklyn man is in police custody, charged with stabbing his relative's ex-boyfriend.
81-year Nicholas Diaz is facing manslaughter charges.
21-year old Kevin Rivera died early Sunday after being stabbed in the chest inside a Bushwick apartment.
Investigators say Rivera was arguing with his ex after their child's first birthday party when the violence broke out.
Diaz allegedly intervened and stabbed the young man.
Rivera was pronounced dead at Woodhull Medical Center.