Dean's first reaction during the start of it was that of waking up in a panic, calling his brother's name. It was an almost instinctive reaction by that point, really. After that faded, however, he slid his hand down his face, grabbed his supply bag, and bolted for the door. Being where he was was no good place to be. Several floors worth of concrete and debris would come crashing down on him in no time, or he'd go crashing through the stairs. Either way, that shit was NOT going to happen on his watch. He hopped down the stairs as they started to crumble.
"Shit, shit, shit, shit..." He said with each step he bounded onto, before seeing Max. Well okay, that's a lie, he saw Girl with Gaping Headwound, too busy with his own panic to really parse features at the moment, but he tugged away any debris which had landed on her and continued his colorful mantra of expletives, only double-timed once he realized who it was, "Max. MAX wake up! Shitshitshitshit. Okay we're gettin' outta here." With one look up the stairs, hoping that Sam was out of the building, he started towards the front door.