It happened just before 11 a.m. on the 2300 block of Bouvier Street.
Police say officers found the girl lying in a back bedroom suffering from a gunshot wound to the right side of her head.
According to the Philadelphia District Attorney's Office, at the time of the shooting, the girl's brother and cousin, both minors, were inside the residence with no adult supervision.
Action News has learned that a 5-year-old boy inside the home fired the fatal shot after a 12-year-old in the home provided him with the weapon.
The girl was rushed to an area hospital where she later died.
On Thursday, the district attorney's office announced charges against the girl's father, 39-year-old Blake Davis, in connection with the unintentional shooting.
Davis is being charged with involuntary manslaughter, endangering the welfare of children, of corruption of minors, recklessly endangering another person and illegal firearms violations.
"I offer my deepest condolences to the Davis family for the terrible loss of a beloved child. This tragedy was 100% preventable. Kids should not be allowed unsupervised access to firearms, period. We can hold both that a father has suffered a horrific tragedy, and that he is also criminally responsible for this loss," District Attorney Krasner said. "As a community, we must also come together to ensure that the two other children found in this residence are able to heal and grow beyond the trauma inflicted on them."
Family and friends gathered at a vigil on Thursday night to remember the young girl.
"These kids with these video games and these Nerf guns, just stop because my son kept thinking she had another life. And he woke up this morning saying, 'Mommy, it's going to be ok, it was an accident, she's going to come back,'" said the girl's mother.