Aggravated manslaughter charges were filed against Jonathan Melendez, 27, who was already being held in the Bergen County Jail on aggravated assault and endangerment charges following his arrest last week.
Investigators seized him after the infants' mother brought them to HUMC on Oct. 23, Bergen County Prosecutor Mark Musella said.
The twins, who'd been in the father's custody in Teaneck, had multiple fractures and head trauma, the prosecutor said.
The one who died at 12:10 p.m. Thursday had been unresponsive, had bleeding on the brain and was initially listed in critical condition, authorities said. The other was listed as stable, they said.
Melendez, a single television production worker, had previously lived with the mother in a subsidized apartment on West Passaic Street, law enforcement sources said.
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