Why Not Stop and Try to Provide Assistance to the Kid You Ran Over?
(SPOILERS) Ruffalo's character did not seem to be drunk or otherwise incapacitated which is often a lame sociopathic reason to flee a vehicular crime scene. His reason to escape was his ex-wife would nag him less hard about the kid's late return. Seriously, the guy makes himself a criminal out of fear the ball breaking mother of his son who will punish him more denying privileges to spend time with his son watching baseball games.
Bottom line. Hurt someone accidentally. Make an effort to help them. Worry about consequences the next day.
He killed sixteen Czechoslovakians. Guy was an interior decorator.