Jason Farmer, 34, was arrested over the weekend for the murder of Angela Montante at the America's Inn and Suites near Beechnut.
Police say he checked into the motel with Montante Thursday, and then killed her during sex.
New details in court Monday morning revealed that Farmer and Montante were having sex in the room when he started choking her. He stopped when she started panicking, but she stopped moving, prosecutors said.
Prosecutors said Farmer waited 24 to 36 hours before calling police.
Police identify man accused of killing fiancee's sister
Authorities found him inside the motel room with Montante's body wrapped in a blanket.
Police say he surrendered Friday night.
Investigators have not said how Montante died.
RAW VIDEO: Jason Farmer appears in court after being charged with manslaughter
Jason Farmer in PC court
Farmer has been arrested several times over the past few years and is a registered sex offender.
According to the district attorney, Farmer had two pending sex crimes against children prior to this manslaughter charge.
One charge is continuous sexual abuse of a child and the other is indecency with a child.
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