In my experience, value for life (both peoples' own life, and the life of others) is directly tied with wealth.

That is to say, poor people don't value living as much as rich people do. They're more likely to engage in behaviour that endangers their own life and the lives of others.

There's a good reason for that: life is cheap among poor people and poor countries because they have little to lose and a lot to gain. The payoff is asymmetric for violence, so it's a rational trade.

There are a few reasons. An important but unfortunate one is that these areas have not received toxic chemical remediation. It is common for adults and children to have complications from lead exposure. A side effect of developmental impairment is increased aggression.

But there are reasons related to a different social culture. The cops and justice system can't help you and may very well ruin your life if you try to involve them, so it's easiest to kill people who slight you. These interactions happen because whatever small amount of money or credibility you might just shrug off is life altering to these people.