As police Inspector Alba Guevara Lopez's officers fanned out through the narrow alleys of a gang-controlled neighborhood in this San Salvador suburb, half had their faces hidden by black ski masks.

"Those who live a little closer are scared that they might be identified and later face reprisals when they're off duty," said the 20-year police veteran, her face visible behind a pair of sunglasses. "In your free time you become more vulnerable."

There is reason to be afraid. Hyper-violent gangs declared open-season on police in this Central American nation in response to a government crackdown that began last year. Killings of officers nearly doubled to more than 60 in 2015, and so far this year 15 officers have been slain, including two on Tuesday. In some cases they are targeted while they're off duty and relaxing with family members, who also become victims.