Leila Fowler was found covered with stab wounds Saturday by her 12-year-old brother. The boy also found an intruder inside the family's home, and the man ran away.
Leila was later pronounced dead at a hospital. An autopsy is scheduled for Monday, CNN reported.
After a thorough search of the Valley Springs home, police said they think they found fingerprints and DNA evidence from the intruder, who they described as a white or Hispanic male with long gray hair, KCRA-TV, Sacramento, reported Sunday.
The man is 6 feet tall with a muscular build and was last seen wearing a black long-sleeved shirt and blue pants.
Calaveras County sheriff's deputies stepped up security at nearby schools and bus stops after the attack, CNN said.
Grief counselors were sent to Leila's elementary school and a candlelight vigil is planned for Tuesday, KCRA reported.