Sacramento County sheriff's Sergeant Jason Ramos says officials suspect that a family member had gang ties.
Ramos said at least a dozen shots were fired from two guns at the house on Saturday night, killing Elvira Campos and injuring her parents. The names of the parents - both of whom are in their 40s and are expected to survive - were not released.
The girl's 14-year-old brother was playing video games in a back room and was not hurt.
Sheriff's officials are also investigating a separate shooting yesterday morning that took place not far from the home.
Ramos said the victim of that shooting - a 32-year-old man who survived - was "definitely a gang member" and detectives were looking at the possibility the shootings were related.