Sam was still there -- thinking he would return home and his brother's corpse would be upstairs while he attempted to summon Crowley to bring him back. Sam wasn't the version he saw on television, the one that got Charlie murdered. The one that put her in the middle of a fight Dean never wanted her in. But he knew his brother and he knew that if there was an opportunity to save him, he would. Dean couldn't really condemn him for that. And the logical part of Dean's mind told him he couldn't. But the more darker part of Dean's mind -- the part that echoed with the Mark said otherwise.
He took the time to contact Liv. That was the smartest thing he could do as he made his way through Storybrooke right after his shift. He was almost lost in his mind, seeing red. Almost literally until Liv's voice pulled him out of the fury and he turned to face her. His brow arching just a tad and gritting his teeth a little before smiling. He did this on purpose. He knew he would regret it and he wanted someone to come over and talk him out of it. Who better than Liv? "You got here pretty quick, Liv. He's not dead yet." Hopefully, Sam would live to fight another day with the person he called in to come talk him down.
Dean barely noticed the blood on her lab coat. More focused on the slight relief at the sight of her. He watched her show a bit, he knew she could take him. And he trusted her to do so. Which said a lot about the friendship they have developed over the last few weeks they had known each other.