PHILADELPHIA (CBS) — Philadelphia police say a 1-year-old baby boy died after being sexually assaulted, and now the stepfather has been arrested.

It happened Wednesday night in Southwest Philadelphia in the 1700 block of South Conestoga Street.

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Police were called around 5:30 p.m. for an unresponsive child. Medics transported the baby boy to Children’s Hospital where he was pronounced dead half an hour later.

The attending physician noted multiple bruises on the child and signs of sexual assault, say police.

Neighbors on the block are shocked by the sudden death of the boy.

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Brande Smith says she often saw the mother holding her son around the neighborhood.

“This woman loves this little boy unconditionally. I just never thought anything like this would happen on our block,” she said. “I can’t imagine what a mother feels when they lose a child.”

Police took the 24-year-old stepfather into custody.

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He is charged with attempted murder, rape, and related crimes.