Pittsburgh police say a man upset that his ex-girlfriend wouldn't name their newborn son after him fatally stabbed her and beat her 72-year-old grandmother to death.

Twenty-five-year-old Cesar Mazza was awaiting arraignment Wednesday on two counts of criminal homicide and a charge of kidnapping.

Police say he took his 3-month-old son from foster care and dropped the baby off at his mother's house May 6. Police say the baby had blood on him and Mazza claimed his ex, 19-year-old Tionna Banks, had tried to stab him.

In reality, police say, they later found Mazza had stabbed Banks 15 times and killed her grandmother Valorie Crumpton.

Their bodies were found May 7. Mazza was taken into custody in New Jersey.

Court records don't list an attorney for Mazza.