Back in the Battleground OR, a nurse is cleaning up Cristina while everyone else tries to fix the damage. She's trying to defend herself for going for the bleeder -- something they normally do -- and tells them she didn't touch the bullet. Hunt just hollers back that when her C.O. tells her to stand down, she stands down. (Also, by the way, let's note here that the explosion happened a split second after she was told to stop and really she couldn't have "stood down" that fast even if she tried to.) Cristina is stunned, and reminds him that they aren't in the Army and he's not her commanding officer. He tries to cover like he didn't just have one of his increasingly recurring PTSD moments and says that he and Teddy are the attendings and she is subordinate and needs to do as they say, using his lecture to explain that they knew the bullets had chemicals that can heat up and explode if they didn't detonate on impact. After this dressing down Callie tries to step in for her friend and tells them that she would have done the same thing, and Teddy tries to end it by saying it's done and they just need to fix it, no use in arguing. She pointedly has Cristina help her out, while Hunt just stares death rays at all of them.
Alex walks up to his brother and immediately Aaron demands to know why he didn't tell his family that he got married. Alex avoids answering by just getting mad that someone told, but Mere assures him it was an accident. Aaron's been worked up into a lather, though, and needles Alex that his friends assumed his own brother would know he was married. When Alex says it wasn't a big deal, Aaron (fairly) counters that it was, but then hits below the belt and accuses Alex of walking out on his wife. The brothers are yelling and drawing a crowd as Aaron taunts that this is going to make their mom go off her meds, while Alex threatens him not to say anything. After some more yelling Aaron declares that he doesn't need his free surgery and Alex at all, and tells Alex he's just like their father who walked out on their family. It's the last straw, and Alex grabs Aaron and demands he take it back. Aaron responds by head-butting him and giving him a bloody nose, so Alex hauls back and punches his little brother in the face.
Back from the break, they're rolling around on the floor in an all-out fistfight, and Bailey runs up and tries to break it up by whacking Alex with some files she was holding. Mere finally gets her arms around Alex and pulls him back, while Aaron taunts him some more about really being like their dad. Mere just orders Alex to walk away, then orders Lexie to not go after him, though she's prancing around like a nervous puppy and clearly wants to go, while Bailey calls for a gurney as Aaron's not doing too well what with the golf ball protruding his stomach combined with the brawl.