I realize that this is a traumatic situation, and it's tough to act correctly when such things happen, but he did exactly what he had to do. While he should not doubt himself, as he acted bravely and correctly, I share his doubt on mankind. I have lost faith in it not only based on violent occasions such as my uncle's and your brother's case, but in how people act toward each other. It's all about satistying our own personal needs without thinking about other people. It's the abusive father, the tiranic boss, the bad teacher, the bully, the guy who cheats on his wife...
About the weapons issue, I could discuss it better on a different topic, but I have to say that if he had a weapon, things would turn out different. Not "could", WOULD. But would it be for better or worse?