SACRAMENTO, Calif. -- A social worker did not follow protocol in the case of a boy who was allegedly killed at the hands of his mother's boyfriend, the Sacramento County Department of Health and Human Services said Thursday.

The department's director, Lynn Frank, said Jahmaurae Allen, 4, was the subject of a Child Protective Services case that was opened on June 16, 2008.

Frank said the social worker affiliated with the case did not follow established department procedures and has been put on administrative leave pending further review of the circumstances.

She released the following statement Thursday:

"Although Child Protective Services intervened in this case and did take some steps to protect Jahmaurae, we could have -- and should have -- done more," Frank said. "In the majority of cases, records show our workers make the right decisions. In the case of Jahmaurae Allen, we did not adhere to our own high standards."

Frank said the social worker did take some steps to ensure the boy's safety, but it wasn't enough.

"I'm really horrified by the situation and by the death of this child. I don't understand how with the focus that we've had, how this could have happened again," Frank said.

CPS said it would implement immediate changes. It will now review all 921 current investigations of children ages 5 and younger; have supervisors accompany social workers over the next 30 days to assess their skills; reach out to law enforcement and other experts to improve the system and accountability of employees; and increase quality assurance reviews from quarterly to monthly.

The Sacramento County Coroner's Office said Allen died of blunt-force head and stomach injuries.

Jonathan Lamar Perry, 26, was taken into custody Tuesday afternoon on suspicion of murder and child endangerment.

Perry was supposed to be arraigned Thursday but did not appear in court because of a psychological condition. He is scheduled to be arraigned Friday afternoon.

He is facing murder and assault charges.