ORANGE, Calif. – A Southern California woman accused of tossing her 7-month-old son from the fourth floor of a hospital parking garage was arrested after she circled back to the scene four hours later, a police spokesman said Tuesday.

The woman’s husband said she has postpartum depression and was hospitalized for it earlier in the summer.

Sonia Hermosillo, 31, of La Habra, was arrested Monday night, hours after the baby was thrown over a railing at Children’s Hospital of Orange County, police Sgt. Dan Adams said.

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

Hermosillo, who could appear in court today, was being held without bail for investigation of attempted murder and is undergoing a psychological evaluation, said Orange County sheriff’s spokesman Jim Amormino. She also was on an immigration hold, he said.

No one answered the door Tuesday at the upstairs apartment in La Habra where Hermosillo lives with her husband, two young daughters and infant son.

Hermosillo’s husband, Noe Medina, told The Orange County Register that his wife had been hospitalized for postpartum depression in June, was taking medication and wasn’t allowed to be alone with the baby.

A witness saw the baby falling through the air just after 6 p.m. Monday and several people called 911. Surveillance video showed Hermosillo’s sport utility vehicle with an empty child seat leaving the parking structure a short time later. The female driver was the only person in the SUV, and the license plate was traced to the Hermosillo home.