As for the OP's point, I don't think the Mother seeing her son for who he is would change him. I don't blame the parents for not wanting to see their child like that, at least they're not in the streets trying to rise trouble over what sounds like a clean shooting. 

 

Bad people are going to do bad things, it's why we need some sort of law enforcement and it's why people should be able to defend themselves at all times. A mother watching the video of their son being killed doesn't change any of that. Now we could question how this man might have been raised and why he became a bad person? That would require a deeper look into the story however. 

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