Authorities announced the charges against 48-year-old Luke Bell on Friday.
Police were called to a home on the 1600 block of East Tulpehocken Street in West Oak Lane on Thursday.
Officers found 80-year-old Crystal Bell dead from a gunshot wound to the head.
Her son, Luke Bell, had been arrested the day before on an unrelated firearms violation.
He's now charged with murder.
The investigation is ongoing.
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