The 12-year-old stepbrother of Leila Fowler told authorities he found his sister murdered and saw a stranger running away.
But now investigators have turned their focus on the family.
The sheriff's department is focusing on the witness account of the step-brother. He was the only person at home when she was killed.
And they've brought in more man-power to find her killer.
More than a week after Fowler was stabbed to death in her family's Valley Springs home; authorities are focusing on the areas nearby.
Sunday, dive recovery teams from the Calaveras and Stanislaus County sheriff's departments searched two reservoirs that sit below the family's house in an effort to find clues.
"It's black water diving, and they're searching the bottom of the ponds with their hands," said Chris Hewitt of the Calaveras County Sheriff's Department. "Because, obviously, in murky water conditions, they cannot see where they're going. So the tenders on the shore, holding the rope, will guide them through the water."
Authorities have knocked on more than 300 doors, asking neighbors if they saw anything suspicious around the time Fowler was killed. Those efforts didn't turn up any more witnesses.
Fowler's step-brother described her killer as a tall man with long gray hair.
A neighbor who said she also saw the man run from the home has since taken back that claim.
People living in the tight-knit community are hopeful the continuing search for more evidence will bring deputies closer to an arrest.
"Sure, we're all concerned. You know, I've got three girls. They're little, they play, well they used to play outside. But since this, now they don't," said family friend Justin Martinez.
On Friday, investigators took knives from the home where Fowler was murdered but won't say whether they were used in the crime.