>> they can't hear nor speak. yet, they serve and protect. it's a group of 20 police officers all deaf mute whose job is to keep an eye in the sky. they monitor 230 surveillance cameras around the clock in the mexican city of oaxaca. for their protection, we cannot show their faces. through an interpreter, the officer tells us she likes her job and is proud of working here, watching over people and protecting her fellow citizens. people here call them silent angels. >> translator: we give them the opportunity to work in public security and we give ourselves the opportunity of taking advantage ...