Necessary? No, the thing would have died on its own, drained as much as it likely had been. Vampires were monsters, though. Not people. Killing them wasn't really difficult for a lot of people. Hell, a year ago, Dean might have done the same thing. It was amazing how perspective could change.

He headed into the house, tracking the people in residence by the heartbeats. Three, by his count. Probably all high, given the pace the hearts were beating. He could hear them talking and laughing long before Sam's ears would have picked up on it.

He followed the sound toward the living room. TV was on loud. Dean and Sam could probably sneak up on them with no trouble.