Homicide is the killing of another person.
Murder requires the proving of intent to kill, or taking some action that could reasonably result in the death of another such as an assault.
If this guy was charged with "murder" then the state will have to prove he had an intent to kill. Just running over the guy will in itself not be sufficient to prove "murder".
But then in the UK....if you beat a Burglar's hind end as he sets fire to your house after raping your daughter.....you can find yourself in jail for assault....so who knows.