Juarez Cartel members execute prison guard...

Juarez Cartel or Vicente Carrillo organization members interrogate prison custody and pressure him to reveal information. The prison custody reveals that he lets inmates go free on night to kill, he also names fellow coworkers linked to organized crime. According to the prison guard he and his co workers work for "Wason" or "Joker"(from batman comic book series) which is a Sinaloa Cartel member. He also states that "AA" or Artistas Asesinos and Mexicles street gangs are aligned to Sinaloa Cartel. Joker is also the chief boss of prison guards in Ciudad Juarez, the prison guard also states that some ex-soldiers from Sinaloa are coming to Juarez city to support Sinaloa cartel.

then they shoot him?

Yeah they find 9mm bullets in his head.