"But immediately following the Vampire’s death, it all switches back on. It’s like he reached a climax by killing the Vampire and now he’s coming down from the high. He doesn’t feel guilty about what he’s done, but he’s aware of it. ... notice his exhale. He breathes like he’s held his breath in the entire time. He drops his shoulders, a sign of relaxation, and indulges in the site of his victim." - Laura, SPN fan I think she nailed it.