Castro has confessed to some of the allegations aginst him, a law enforcement source closely involved with the investigation told CNN on Thursday.
Authorities have also been reviewing a lengthy document described by a law enforcement source as "more of a diary" in which the source said Castro cites being abused by family members as justification for his actions.
On Friday, they boarded up his Seymour Avenue home to preserve the crime scene, said Cleveland's deputy police chief Ed Tomba. Authorities plan to later erect a fence around the home.
The ordeal has rattled neighbors like Juan Perez, who had viewed Castro as a "very social, happy-go-lucky ... good guy" but now think just the opposite.
"We feel lied to and we're ashamed because we couldn't help earlier," an emotional Perez told CNN on Friday. "... I just can't put it all together still."