juan pablo parez satillan was shot near matamoros just two months earlier. in 2011, in tijuana, a witness says jose alfredo yanez reyes was killed for using his cell phone to record an agent beating a migrant. and sergio hernandez guerica was shot between the eyes under a bridge in juarez. in each case, the border patrol justified the killings saying they were threatened by rock-throwers. but getting them to speak on the record about anything at all proved difficult. >> hi bill, this is wab knew calling from al jazeera english. we're down in nogales az right nowso i'm just calling to see if we would be able to arrange an interview and a ride along with an agent out here. >> well, we've sent emails, about, starting about six weeks ago. >> and why is that? >> yeah. >> yeah, it just seems a little opaque like i'm just trying to understand why the request was declined. >> what's happened is that with the border patrol being one of the largest law enforcement agencies in the country, they work with a population that doesn't work back with them. they're not like a