On Friday night, police confirmed a woman was arrested in connection with the case. She'll be identified once she's formally charged.
The gunfire rang out around 5:51 p.m. Thursday on the 4000 block of Meridian Street in the city's Holmesburg section.
Video obtained by Action News shows the gunman walking up and opening fire on a baby and his parents outside of a home.
The infant was shot in the leg by one of the bullets.
When police arrived, they said the baby's parents weren't there. It was a good Samaritan neighbor who took the baby to the hospital.
"We're very lucky that 7-month-old boy is in stable condition," said Philadelphia Police Chief Inspector Scott Small.
7-month-old boy shot by stray gunfire in Philadelphia's Holmesburg neighborhood
Police say the parents, who were not hurt in the shooting, don't live in the area and they're not sure why they were in Holmesburg.
Neighbors are glad the baby survived.
"I work with children. I'm a day care teacher, so it hits home," said Bobby DelPiano, of Northeast Philadelphia.
Anyone with information is asked to call police at 215-686-TIPS.
RELATED: Check the 6abc Neighborhood Safety Tracker