From an article in The New York Times:
Human rights advocates and opposition politicians have taken the two sets of killings [of three Salvadoran congressmen by Guatemalan national police, and subsequently, the murder of the killers four days later in prison] as proof that criminal gangs have corrupted Guatemala’s national police force and that groups of officers are operating like drug syndicates, robbing and killing competing dealers.
A high-ranking United Nations official here, who requested anonymity to protect his diplomatic neutrality, said he believed the Interior Ministry and the National Police created death squads over the last three years, trying to combat the wave of violent crime by gangs like the notorious Mara Salvatrucha, a group started in Los Angeles by the children of Central American civil-war refugees of the 1980s.
The officers in those squads belong to evangelical churches, the official said, and see the extrajudicial killings of gang members, known here as "social cleansing," as holy work. But they have also begun to commit crimes for their own profit. "It gets out of their hands," the official said. "They create a Frankenstein."