A woman accused of killing a 7-week-old boy last month in Mililani is the boy's aunt who has her own infant, a 3-month-old daughter.

Honolulu police charged Natalee K. Westbrook, 26, with second-degree murder Wednesday. They released her after she posted $150,000 bail. Westbrook is scheduled to make her first court appearance on the charge Monday.

The boy's mother told police she dropped off her son at her sister's home on May 9.

Westbrook told police she and her nephew fell asleep on her couch with the boy on her lap. After she woke up to go to the bathroom, she said she found the boy on the floor face down and not breathing.

A neighbor told police he performed CPR on the boy after Westbrook alerted him to what happened and asked for help.

An ambulance took the boy to Wahiawa General Hospital. The boy was later transferred to Kaiser Moanalua Medical Center, where he died May 10.

At the time the boy was pronounced dead, homicide detective Kenneth Higa said he saw a large bruise on the left side of the boy's head. He also said the doctor indicated the boy may have suffered internal bleeding to his skull and semidetached retinas in his eyes.

Police classified the case an unattended death after the Honolulu medical examiner performed an autopsy but deferred making a cause-of-death determination. They reclassified the case a murder after the medical examiner later determined the boy's death a homicide due to abusive head trauma.