Criminal Minds, Season 7

Prentiss:
We saw the bodies, all of them have stress breaks in the same places.

Rossi:
That's consistent with years of fight training.

Hotchner:
Fight training. You think he's a boxer?

Rossi:
It makes sense. A fighter would have the endurance it takes to commit this kind of overkill on this many people with a pipe or with his hands.

Morgan:
It would explain why at the first crime scene he lined the bodies up in the corner, like in the ring.

Hotchner:
It makes sense about the bloodlust, but what triggered the killings?