"Unless something very glaring comes out during the course of the investigation today, it seems to be just a very, very tragic incident," said Lt. Dave Coleman with the Los Angeles County Sheriff's Department.
Investigators say the baby's father, who had left the house, called authorities to the home on Cliveden Avenue in Carson just before 3 p.m. when he realized he had left his son in the hot SUV, still strapped in his car seat.
Responding deputies smashed the window to get the baby, but it was too late.
It's unclear how long the baby was in the SUV. Investigators say the couple has five or six children.
Friends say the father is a loving man who would never do anything to intentionally hurt any of his kids.
Detectives say it will be up to the district attorney to decide if the father will face any charges.
CORRECTION: The baby's age was initially reported as 4 months, but L.A. County Coroner's Office confirms the baby was 5 months old.