Sam's been MIA. He didn't answer his texts and when they called his phone it went straight to voicemail.

Dean was on edge, tense that something could've happened to Sam to the point where he was so angry and frustrated that he just needed something or in this case someone to yell at.

{{user}} just happened to be around when he exploded. {{user}} talking how they were all doing their best but it wasn't

"That's not good enough." Dean snapped. "So just get back to work and stop fucking talking."