I guess it might depend on when the story occurred.
10+ years ago, "look both ways before crossing the street" wasn't drilled into people's heads.
After tragedies and everything else, I doubt anyone living in the U.S. has not learned this particular 'phrase' from parents or schools.
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Based on behavior of the child, he may have had a form of ADHD. If he did have other problems, I don't see the Dad being that careless towards him.
During the actual 'balloon' scene, I thought he was going to be kidnapped/attacked or something along those lines and not phantom hit by a car. The car didn't hit the son, the dad 'made' it, etc. etc. but the story they wanted to tell needed the following to happen:
1. Son dies tragically.
2. Dad's fault
3. Mom divorces Dad.
4. Dad has mental 'scars' from the accident.
5. Origami killer sees it all.
Given these parameters, there isn't much else they could have done to tell their story.
I do agree, that there is a big disconnect between what they showed and what happened. If they had just showed him 'jumping' and then cut before he reached the son then I would have totally accepted that he didn't make it but got hurt from jumping out to save his son.
Him jumping AND making it... and then son dying anyways just seemed wtf to me.
C