LOS ANGELES - A woman who decapitated her 4-year-old son with a kitchen knife showed signs of mental illness months before the attack but child welfare officials decided she did not pose a serious threat.
Lars Sanchez was found decapitated last month in his bedroom.
According to documents released by the county Department of Children and Family Services, Tijerina was investigated nine months earlier after screaming and shouting "I think you killed my son" outside the boy's Highland Park preschool.
The principal at Meridian Children's Center reported her to the county's child abuse hotline.
Child welfare and mental health officials investigated, but decided not to remove the boy from his home.
According to the documents obtained by the L.A. Times, the investigation concluded that the mother's "emotional stability, developmental status or cognitive deficiency impairs her current ability to supervise, protect or care for the child."
However, officials concluded that any risk to the boy could be addressed through informal monitoring by relatives and neighbors.
The employees involved in the case have been assigned to desk duty pending a review.
Last month, county supervisors voted to review the deaths of about a dozen children who had been the subject of abuse complaints to the county.
The vote followed the July beating death of 6-year-old Dae'von Bailey in South Los Angeles.
His mother's ex-boyfriend is suspected of killing him.
The boy reportedly had been the subject of about a dozen calls to child welfare authorities about possible abuse.
Last year, social workers removed 4,468 children from Los Angeles County homes, and parental mental illness was the main reason in nearly a fifth of those cases.
However, mental illness alone doesn't disqualify a parent from caring for a child.
Social workers must also determine if the child is being abused or neglected, the parent is getting treatment, and whether there are other adults at home to care for the child.
The decision can be difficult.
"Social workers are not necessarily trained to assess a parent's mental health," said Charles Sophy, medical director with the Department of Children and Family Services.
"Mental illness is easy to hide sometimes," Sophy said. "You can put on a smiling face when I knock on your door, and I will never know that you tried to kill yourself last week."