Clark enters and pulls back the sheet on Mandy, who miraculously doesn't fucking jump out of her skin in fear. The sight of a "dead" body only serves to make Clark more unhinged and overcome. "This is too much," he tells himself, between sobs. He keeps repeating "Okay, okay" to himself, and seems like he's about to head back onto the floor when something clangs in the bathroom. We don't see Percy, but Bailey's face has panic enough for everyone. From her POV, we hear Clark open the door, we hear Percy beg him not to shoot, we hear Clark ask him if he's a surgeon, and we hear him ask it again. "Yes, sir, I am," Percy says. And then he begs. And then Clark shoots. Bailey covers her mouth to keep from screaming, and now she sees Percy, fallen to the ground, wide-eyed and convulsing. Looks like he's been shot in the gut. Bailey grabs at her face to keep from making a sound. She's staring at Percy, waiting for Clark to leave so she can help him, when she gets pulled out of the frame. That was a good shot to include in the promos and it's a good one here. Holy crap. Clark points the gun at her and asks if she's a surgeon. She can barely form words, and it looks like she almost says "yes," but ultimately she's able to stammer "No! No... no... I'm a... I'm a nurse!" I do not like seeing Miranda Bailey whimpering and begging for her life, I'm just gonna say that. "I'm sorry," Clark says, as he reloads, "for the trouble... for the mess." Is that an "I'm about to shoot you" I'm sorry, or what? Bailey's clearly not sure. But Clark just says he's sorry again and walks out. From her bed, Mandy finally breaks, while Bailey exhales in relief, fear, horror, and shame ("a nurse") all at once. Meanwhile, Percy's bleeding out. Act break time? Oh yeah.
Back with Alex and Lexie, Mark uses his most soothing voice (non-panty-dropper division) to prepare Alex for the uncomfortable reality that he needs to put in a chest tube. Alex is not enthused. They go in through his side, armed with disinfectant but no anesthetic, so of course Alex starts screaming bloody murder. So here's the scene: Mark is shoving a chest tube through Alex's side, Alex is screaming like his limbs are being cut off with a Swiss army knife, Lexie is understandably upset by the situation, and Mark is intermittently yelling at Lexie to "SHUT HIM UP" lest the shooter hear and come to finish the job. Lexie talks soothingly to Alex, and that works for a moment ... until the tube comes into play, at which point Lexie needs to shove a towel into his mouth. Whatever works.