A Montgomery County man who shook his infant daughter to death was sentenced this week to eight-to-16 years in prison.

Craig Baylis, 31, pleaded guilty Wednesday to third-degree murder and endangering the welfare of children during a hearing before County Judge William Carpenter. Baylis, a resident of Norristown, admitted to killing his 6-week-old daughter, Mackenna, while caring for her last February.

Mackenna’s mother had called police after coming home from a doctor’s appointment and finding the infant gray and lifeless, according to the affidavit of probable cause for Baylis’ arrest.

The girl died about an hour later at Einstein Montgomery Hospital. An autopsy conducted by the county coroner found that Mackenna had died from “inflicted head trauma,” likely from “vigorous movement of the head while relatively fixed in relation to the neck,” the affidavit said.

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Her mother told detectives she was at an appointment and had left Mackenna alone with Baylis, the affidavit said. Baylis had called her to tell her the baby had hit her head and suffered a nosebleed but was fine.

Baylis initially told police that Mackenna had fallen out of bed and hit her head, according to the affidavit. He later recanted that statement, saying he had fallen asleep while holding the baby, and had awakened to find her facedown and unresponsive on the bed. He admitted to detectives that he had shaken her in an attempt to rouse her, causing the fatal injuries.