Court records say 30-year old Jesus Castillo-Dimas laughed at his ex-girlfriend and taunted her as she kneeled over their boy's body after he had run him over.
Castillo-Dimas is charged with murder in the death of Yandel Castillo-Castillo.
He's also accused of trying to kill the woman and her new boyfriend.
Castillo-Dimas is being held on a $1-million cash bond.
Police say he was upset the boys mother had started a new relationship.