The child landed on concrete, police said. He was hospitalized in critical condition at UC Irvine Medical Center.
UPDATE, Aug. 24, 1:40 p.m.: The 7-month-old baby died Wednesday, according to the Orange Police Dept.
La Habra resident Sonia Hermosillo, 31, was arrested at about 10 p.m. Monday.
Police said she was taken into custody after officers spotted her driving by the scene hours after the crime was committed.
"Our investigators are sure that we have the right suspect in this case. We do think it was done on purpose. We don't think it was an accident," said Orange Police Sgt. Dan Adams.
It was unclear what she was doing in the area at the time. Police said she was very cooperative.
"I'm describing it as stoic, not much emotion. Actually no emotion at all," said Adams.
Hermosillo's tan 2000 Chevy Blazer was caught on surveillance video leaving the parking structure immediately after the incident around 6:20 p.m., according to police.
Investigators don't think the crime was caught on tape, but at least one witness saw the baby falling.
"The one witness that was walking by did say that he was falling. So whether or not he was dropped or thrown is a question that I don't have an answer to," said Orange Police Sgt. Dan Adams.
Hermosillo's husband had reported her and their child missing Monday night, police said. When she was eventually stopped outside of the hospital, officers found an empty car seat in her vehicle.
Officials are searching through records to see if the 7-month-old was a patient at Children's Hospital.
"There is a driveway right there where the child landed. As far as how he actually survived the fall to remain in critical condition right now, I really don't know," said Adams. "This is a defenseless child who is now clinging to life in a local hospital."
Hermosillo was arrested on one count of attempted murder and was held at Orange County Bail without bail. She is scheduled to make her first court appearance Wednesday.
UPDATE, Aug. 24, 1:40 p.m.: The 7-month-old baby died Wednesday, according to the Orange Police Dept. Hermosillo's charge of attempted murder will be amended to a charge of murder, according to police.