Root causes of this particular incident? The possession of deadly weapons by people who rarely have a legitimate need to have them beyond "MY RIGHTS" and "SECOND AMENDMENT". This has nothing to do with poverty.
I don't think any kind of punishment could effectively deter this because I don't believe this was intentional or that the perpetrator even imagined that the bullet could still kill someone despite the distance and obstacles on the way. Not to mention that as another comment points out, capital punishment is a thing and that still isn't enough to deter murder/etc.
The main problem here is that people have access to and an obsession with deadly weapons. This obsession leads them to acquire those weapons even when they have no legitimate reason to own/carry them. Accidents are bound to happen even with trained users, but typically the risk is worthwhile when you have a legitimate need to own/carry the weapon. When you don't have a legitimate need however, it's just needless risk-taking that will eventually produce situations like this.
I don't think any kind of punishment could effectively deter this because I don't believe this was intentional or that the perpetrator even imagined that the bullet could still kill someone despite the distance and obstacles on the way. Not to mention that as another comment points out, capital punishment is a thing and that still isn't enough to deter murder/etc.
The main problem here is that people have access to and an obsession with deadly weapons. This obsession leads them to acquire those weapons even when they have no legitimate reason to own/carry them. Accidents are bound to happen even with trained users, but typically the risk is worthwhile when you have a legitimate need to own/carry the weapon. When you don't have a legitimate need however, it's just needless risk-taking that will eventually produce situations like this.