>> just what you explained here, can you bring that a little bit. does this make a difference when someone comes in, if you have this sort of shrapnel, whatever, if the bullet is intact? does it make a big difference as to what's left in there? >> it's a through and through injury it does make a difference. have you a significant amount of energy from that bullet. if that energy passes through the brain and comes out the front, some of the injury is going to dissipate in air as opposed to within the skull cavity. if all of that energy from that bullet is being sort of distributed in the brain, that's a much worse injury, so the fact that it goes through and through in this case is a better sign for her. >> dr. sanjay gupta. the mass shooting in tucson is not the first incident that's given the state of arizona negative headlines. some recent controversies next. ♪ ooh, ah la, la, la ♪