Is the "serial killer" that Sonya and Marco are chasing also "The Beast" in Juarez?
On the surface, it would make sense to assume that they are the same person, but I don't think they are. The serial killer seems to be reacting to the lack of concern or investigation into the Beast's killings. He's making a political statement about the differences between how killings are treated in El Paso versus those in Juarez. If he was responsible for the deaths, why would he care?
Plus, there is the new cover-up in the FBI to consider. Is one or both of the killers in law enforcement? Could it be someone we already know?