12 gang members were killed late Monday afternoon when gunmen with assault rifles burst into a local youth prison. Witnesses say the gunmen were also throwing hand grenades, firing rounds, and even decapitated one victim. 11 inmates were sent to the hospital, citing gunshot and hand grenade wounds. Prison officers were unarmed, due to Guatemalan law that restricts weapons, leaving the facility unprepared for the attack.

Officials report that this is the latest clash in a conflict between the Mara Salvatrucha and Mara 18 street gangs in Guatemalan prisons. An unnamed prison officer said that all of the victims were from the Mara 18 gang, while the attackers were from the Mara Salvatrucha gang.

Although the gangs had an agreement not to fight while in jail, the treaty collapsed last month and violence has resumed. In August, three gang members were killed as a result of seven simultaneous prison riots. Officers note that these gangs are extremely violent, depicting a scene of splattered blood and corpses left at the youth prison. An AK-47 assault rifle, a 12-gauge shotgun and three handguns were found in the prison courtyard.

Guatemalan officials are asking plenty of questions. A local judge had recently ordered police to send 10 officers to watch the jail around the clock because he feared another outbreak of violence. At the time of the attack, no police officers were present in the jail.