What's driving Guatemala's surge in gang violence?

The murder of 10 police officers last week in retaliation for the put-down of a prison mutiny caused deep shock in the Central American nation of around 18 million people. The standoff began when gang members took dozens of guards hostage at three prisons to demand that incarcerated gang leaders be moved from a maximum-security prison to more lenient facilities. A day later, the police and army entered the prisons to restore control, triggering retaliatory attacks on the police blamed chiefly on the powerful Barrio 18 gang.