The words what have you done this time, Shawn? are in his mouth, he can even taste their familiar ring. But recognising the serious panic in Shawn's face he decides to do as he's asked.

Besides, IRS, that scares the hell out of him.

"What's going on?" Gus tries for a neutral approach to the situation. The less he says, the less he can get into trouble for.

Shawn is still standing with an arm around his waist though, so this is probably a big deal, Gus puts one arm across Shawn's shoulder with the hope that this is the right move.

On the other hand, this could just be one of Shawn's pranks, if so, he's going to kill Shawn later.