Yesterday, Reuters came out with an article on vigilantism in Guatemala, a consequence of the on-going gang problem. This is not the first report of it kind. There have been similar reports focused on other countries in Central America. El Salvador comes to mind (though I can't locate that article).
The gang problem in Central America does not get the type of serious attention and consideration it deserves. It is a slow-motion train wreck with significant implications for human rights, governability, democracy, and to some degree, even US security. Whatever gains have been made since the end of the wars in Central America, they are threatened by the gang crisis. Vigilante groups could easily evolve to into gangs. Police can easily be, and have been, involved in extrajudicial killings. Impunity can be rampant. In nearly all of these countries the military is operating in "support" of police forces, without adequate legal authorities, command and control mechanisms, and competent judicial structures. This is bad juju and it does not take much imagination for this scenario to spiral into failing state category.