The mother, who was not identified, told police that her son was sleeping when she parked at the Parkview Community Hospital Medical Center for a doctor’s appointment, The Press-Enterprise reported.
She left the SUV’s doors unlocked and the air conditioning running while she went to her appointment, police told KTLA.
"Even when it's running and it's comfortable in there, it's unlocked and there's a chance of the car being stolen, or something happening to the child," police spokesman Officer Ryan Railsback told KNBC.
Police said they found the boy sleeping, but unharmed in the RAV4. Officers told KTLA that the 24-year-old mother could face felony child endangerment charges for the alleged incident.