miles from the compound where the hostages are held. about 40 special force commandos, mostly navy s.e.a.l.s, move undetected over the rough terrain. but suddenly, everything goes wrong, when just 300 feet away, they are exposed, maybe by a barking dog. a firefight breaks out. and as a u.s. drone watches overhead, one terrorist runs back inside and shoots both hostages. u.s. forces kill five aqap terrorists. the rest flee. and in one of the most dangerous parts of the mission, a combat medical team needs to spend a tense half hour on the ground, trying to stabilize the two gravely wounded men. finally, they are flown back to the "uss makin island" off yemen's coast, but one dies on the way and another dies on the ship. >> you have to really look at this from a surgical point, just like a heart surgeon or a brain surgeon. some will live, some will die. >> reporter: as word of the failed rescue mission leaks out,