When the compulsion didn't take, he looked at her funny. And listened. No wonder it didn't work. She wasn't alive. He didn't hear a heartbeat. That was almost a relief for him, because other wise, it meant she did something to herself to resist. Because he was at full power, his best yet with the steady diet of blood for the past couple days since reversing the mess that Dean created.
"You've got more explaining to do than me. Why isn't your heart beating, Caroline?"