Troopers responded to the 7000 block of Lancaster Avenue in Tulpehocken Township around 11:30 p.m. Friday, Pennsylvania State Police said.
Scott Albrecht, and his 40-year-old girlfriend, were arguing while Albrecht was holding the baby, state police said.
He then threw the baby to the ground, causing serious injuries to the baby's head, according to state police.
The victim was taken to Penn State Hershey Medical Center for further evaluation, authorities said.
Albrecht was arrested and charged with aggravated assault, simple assault, recklessly endangering another person, endangering the welfare of a child, and harassment.
The investigation is ongoing.
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