The unidentified boy was playing with a cigarette lighter when he started a fire that torched two vehicles and a trailer that belonged to a church, a fire captain said.
The infant was estimated to be 12-18 hours old.
A second child has died as a result of a condominium fire that killed his mother and older brother earlier this month.
A Stanton man died late Friday night following a crash earlier in the day in Huntington Beach, authorities said.
Students and teachers were forced to evacuate Monday when a fire broke out at a Jewish elementary school and temple in Aliso Viejo.