Factual error: Current flows in a circuit. The guy on the metal antenna tower is similar to a bird sitting on a power line. No current flows through the bird. Furthermore, current would flow from the transformer through the water to ground. There would be no current flow up the metal antenna tower.
Continuity mistake: Minnie Driver helps Christian Slater escape from the prison by unscrewing a metal cage. Right before she is finished unscrewing there is an underwater shot of the cage already broken through. Cut to the next shot and she frees the cage again.
Answer: Because the Sheriff wanted to kill everyone, leaving no witness. Remember the old saying, "The Enemy of my Enemy is my Friend."