Someone imitating a famous serial killer, like Ted Bundy or Jeffry Dahmer. And I mean immitation to a T. Something as brutal as what those two did would make for some great TV drama.

Also:
-A serial killer who targets famous people. Maybe it would explain why so many celebrities died in 2009 lol.
-Cannibalism, but the killer uses their dog as a partner in crime. Like, they make the animal help in their kills and parttake in the cannibalism.
-Chainsaw murderer!
-A massive school shooting and the guys have to go in and stop the kid before anything else bad happens.