It happened around 9:30 p.m. near Cypresswood.
The man and child were on foot when a southbound Toyota Camry hit them, HCSO said.
The driver of the Camry cooperated with investigators as they looked into what happened.
The man killed, identified as Nicholas Arriaga, had crashed his Jeep into a concrete wall and got out of the vehicle with his child before attempting to cross the lanes on foot, investigators said.