District attorney's spokeswoman Sandi Gibbons said the victim's 13-year-old cousin is facing charges of murder and attempted murder in juvenile court.
Officials said the incident may be linked to gang activity, the Los Angeles Times reported Wednesday.
Jasmine Sanders, 8, was hit in the chest with a stray bullet last Wednesday while playing near a south Los Angeles apartment building with a group of youths, the newspaper said.
The victim's mother, Shadonna Kinney, 28, said she attempted reviving her daughter after the shooting.
Onlookers said a male teenager opened fire at a group of young men near the apartment building.
Neighbors, law enforcement officials and members of the community took part in a vigil Thursday for Sanders, the Times said.