That's very interesting. The only thing I've ever heard of that can transmit craziness like that is a parasite that comes from cats. https://www.theatlantic.com/magazine/archive/2012/03/how-your-cat-is-making-you-crazy/308873/ I think it can spread from person to person without a cat involved, but cats are where it comes from. The symptoms include fits of rage and extra risky behavior.
RE: Gun Violence Is NOT A Mental Health Issue It's A Culture Issue