"Whoever these gunmen were, they were directly outside the front door," Sacramento County sheriff's spokesman Sgt. Jason Ramos said Sunday. "This was not a drive-by. These gunmen approached the house and shot inside."
Sacramento County sheriff's officials suspected that a family member had gang ties.
"You have to be hard pressed to think a 10-year-old girl was the intended target," 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, Ramos said. The names of the parents - both of whom were in their 40s and were 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.
Detectives were canvassing the neighborhood for possible witnesses and forensic units were gathering evidence at the home Sunday, where a cluster of bullet holes marked a front window and more holes were found in the front door and a window frame.
The family had lived in the home in an area about 11 miles northeast of downtown Sacramento for less than a year, Ramos said. There were no records of sheriff's officials being sent there previously, he said.
"I can't even imagine what would bring people to do that," neighbor James Corbett told The Associated Press. Corbett, who lives about three houses down from where the girl was shot, described the neighborhood as quiet, with a "bunch of young families."
On Sunday morning, about a half dozen grieving relatives arrived at the home, The Sacramento Bee reported.
"We have no idea what happened - she was a very happy little girl," Tony Reys, the uncle of the girl, told the newspaper.
Sheriff's officials were also investigating a separate shooting Sunday morning that took place not far from the home. 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, Ramos said.