Mark Spatucci, 22, is accused of killing his ex-girlfriend with their 10-month-old baby in the room.
Investigators say he broke into the Waldwick home Tuesday night where 23-year-old Mary Greff, a former Miss New Jersey Teen USA contestant, lived with her parents.
She was believed to have been strangled, though autopsy results were pending.
Her body was not found until at least 12 hours later.
Prosecutors said Greff and Spatucci began dating two years ago, that she gave birth in February and that the two had lived together for a short time before she split from him and moved in with her parents.
Investigators believe Spatucci drove to the Greff residence late Tuesday and entered, undetected, through a second-floor window. Once inside Greff's bedroom, prosecutors say an argument turned violent and Spatucci killed her, leaving the body on the bed.
Greff's parents were believed to be asleep in another part of the house. Her father found her dead early Wednesday, police said.
Prosecutors said Spatucci had court-ordered custody visitation with the infant, but Greff had full custody.
Spatucci was located late Wednesday in Midland Park and taken into custody for questioning.
He was charged Thursday with murder, felony murder, burglary, endangering the welfare of a child and hindering apprehension.
Spatucci is being held on $2 million bond.
(The Associated Press contributed to this report.)