A California woman tossed her 7-month-old baby from the fourth floor of a hospital parking structure on Monday, police said. Sonia Hermosillo, 31, of La Habra was arrested after she circled back to the scene four hours later, police said Tuesday.

Hermosillo was taken into police custody on Monday night, hours after the baby was thrown over a parking structure railing at Children's Hospital of Orange County, Orange Police Sgt. Dan Adams said.

The infant remained in critical condition on Tuesday at the University of California, Irvine, Medical Center.

According to an Associated Press report, the woman's husband, Noe Medina, told The Orange County Register in an interview on Tuesday that his wife had been hospitalized for postpartum depression in June after she said she didn't want their son, Noe Jr., who was diagnosed with congenital muscular torticollis - a twisting of the neck to one side.

The baby wore a helmet to correct his plagiocephaly, also known as flat-head syndrome. It was unknown if the infant had the helmet on when he was tossed over the railing.

Hermosillo was being held without bail for investigation of attempted murder and is undergoing a psychological evaluation in the jail's medical ward, said Orange County sheriff's spokesman Jim Amormino.  She also was on an immigration hold and could make a court appearance as early as Wednesday, he said.

Hermosillo and her husband have two daughters and the baby boy. According to neighbors, Hermosillo was a spirited and lovely mom with her girls.  

She was very happy when she was pregnant with her baby, neighbor Sonia Herrera, 40, said.

But after the baby was born, Hermosillo changed suddenly and seemed depressed, Herrera said. 

Medina told the Register that his wife didn't look at their son as normal and didn't accept that he was like this. Medina added that in recent weeks his wife seemed better and he began to trust her.

Hermosillo was not allowed to be alone with the baby while she was undergoing treatment. But she grabbed him Monday while Medina was watching their other two children.

A witness said that he'd seen a baby fall from the parking garage shortly after 6 p.m. He called 911 around 6:20 p.m. Using surveillance video, investigators focused on a 2000 Chevy Blazer that was seen leaving the garage minutes after the incident. The Blazer was linked to Hermosillo.

During the investigation, police had received a call from Medina reporting that his wife and son were missing. Hermosillo was arrested without incident when she returned to the scene a couple of hours later. She was cooperative with authorities, said police.

Police have not yet released a motive. Orange County court records indicate that Hermosillo has no major criminal record but pleaded guilty to four traffic violations in La Habra in 2008, including driving without a valid license and having no proof of insurance, reports the Associated Press.