As a soldier myself, my training has taught me that it is entirely possible what was described. Perhaps you've seen too often where you drop someone in a similar fashion in a video game and they just go right down. If you read the book Black Hawk Down, you will understand this better. A problem they had in Somalia was that they were using armor piercing rounds of a small caliber and they could shoot a Somali 3, 4, 5 times or more and the round would go right through them, leaving a nice hole and they'd keep coming anyway. Adrenaline is a powerful drug. Do you remember the scene in the beach invasion in Saving Private Ryan? There was a part in there were a soldier reached down and picked up his own severed arm and carried it around. Severe trauma combined with unnatural events (war) and adrenaline make unbelievable things happen. Add in some powerful drugs such as cocaine and god knows what else those guys were on and you get some pretty hard to rationalize stuff. In my Combat Lifesaver classes, we were actually taught that a soldier may in fact lose an entire limb and continue to fight as if nothing happened until they bleed out. We were trained by a Combat Medic who saw time in just about every major conflict since Vietnam before he retired shortly after Desert Storm. He had similar stories, too many to recount. It does happen, it did happen the way he said it happened. There are less publicized articles on the 'net about Operation Iraqi Freedom if you look for them. They give you things like the first story I linked that you didn't hear on CNN, Fox, or MSNBC.
I'm not taking offense to your disbelief BTW. I am trying to let you know that what you seen in BHD, We Were Soldiers, Saving Private Ryan, etc. are very real and happen in real combat. Those things are not simply theatrical in nature to up the ante.