They were given one of the most dangerous orders in policing: Take down MS-13.
They were bankrolled by the United States and trained by FBI agents.
But members of the Salvadoran police have been killed by the dozens in each of the past three years, most in attacks that investigators and experts blame on MS-13, an international street gang. At least nine officers were killed in the first month of this year.
Now, a number of El Salvador's police officers are fleeing the gang they were tasked with eliminating.