PHILADELPHIA (AP) — Authorities say an elderly woman sleeping in her Philadelphia home escaped serious injury when she was struck by a stray bullet fired from outside the residence.

Juanita Fortune says she heard the gunshot around 1 a.m. Monday, but didn’t realize she had been hit until she saw a shell casing next to her bed. The bullet didn’t pierce the 72-year-old woman’s skin but did leave behind a painful bruise the size of a melon on her right knee.

Fortune’s 38-year-old grandson was also in the home at the time of the shooting but wasn’t injured.

Authorities say it’s not clear who fired the shot or if the shooter was targeting Fortune or her grandson.