SANTA ANA, Calif. -- Arraignment was postponed Thursday for a La Habra woman accused of throwing her 7-month-old son from the fourth floor of a parking garage at Children's Hospital of Orange County, then walking into the hospital to have her parking validated before driving away.

Her bail was set at $1 million but 31-year-old Sonia Hermosillo, who is believed to be an undocumented immigrant, is also subject to an immigration hold. Her arraignment was rescheduled for Monday.

Hermosillo's son, identified as Noe Medina Jr., was taken to UC Irvine Medical Center. He was taken off life support on Wednesday afternoon. Police and prosecutors said he was thrown from the fourth floor of the structure -- about 40 feet -- at 455 S. Main St. around 6:20 p.m. Monday.

In addition to murder, Hermosillo is charged with assault on a child with force likely to produce great bodily injury resulting in death and faces up to 25 years to life in prison if convicted.

Hermosillo is being held in isolation and under suicide watch in a jail medical ward and undergoing a psychiatric evaluation.

The boy, who has two sisters, suffered from a medical condition that required him to wear a helmet. The child had regular appointments at CHOC, but he did not have one on Monday, authorities said.

According to authorities, Hermosillo removed the child's helmet and dropped him from the fourth floor of the parking structure. She then walked inside the hospital to get her parking validated, then left the scene, authorities said.

Hermosillo's husband, Noe Medina, told reporters at UC Irvine Medical Center Wednesday that his wife suffered from postpartum depression and had rejected the baby because of his medical condition.

"She didn't know what she was doing," he said in Spanish through an interpreter. "Please don't judge her."

Orange County Deputy District Attorney Scott Simmons said Hermosillo's decision to remove her son's helmet showed there was more than postpartum depression at play.

"It shows her intent to kill the baby," Simmons said.

The break in the investigation came when Medina contacted La Habra police about his missing wife and son. La Habra police then called the Orange police about the report, Sgt. Dan Adams said.

The license plate of a tan 2000 Chevy Blazer was captured on video surveillance tape at the parking structure, Adams said. Detectives determined that Hermosillo had been driving a vehicle that matched the one seen in the surveillance footage.

At 10:15 p.m. Monday, Hermosillo's vehicle was seen by an Orange police officer being driven past Children's Hospital. The officer stopped the Blazer and detained Hermosillo. An empty child seat was found in the vehicle, Adams said.

A fund was established to help pay for the boy's burial. The Wells Fargo account number is 1584897597.