This is a realtively common malfunction with AR's. The primer pockets were probably a little loose on those cases resulting in a primer blowing out of the pocket and skewering itself onto the protruding firing pin. maybe they use pistol primers?
Then as the action cycled it stripped another round and fed it to the chamber, but the bolt could not go into battery due to the blown primer being in the way. The gun could not fire in this condition. And it probably was made worse when they tried to cycle the bolt and stripped another round and shoved it in behind the first creating a double feed.
This is one of the shortcomings of the AR design. They also have a tendency to try to simultaniously strip two rounds off the mag and shove them into the hole, wedging both.
The correct action to clear a type 3 malfunction is to lock the bolt open, drop the mag, and if the bolt will move full travel then rack rack rack reinsert mag and rack.
If the bolt will not go full travel it means something is stuck in the hole and you must lock the bolt open and using your support hand, (so you don't inadvertantly release the bolt onto your trigger finger) stick your fingers into the mag well and fish around until you have removed all offending debris,and the re-load the gun.
IN the case of the blown primer scenario, the bolt would not close all the way after you cleared the gun and tried to reload it. At that point you have a broke gun and it's time to either run or get the pistol out,,, or both.
It should have taken no more than 15-30 seconds to figure all this out. If it took longer you're probably dead.
This is the reason why we go to shooting schools, so we can learn how to deal with this type of stuff. UNfortunately most people don't attend these schools, and as a result we have less than trained individuals at our ranges. Rereational shooting does not mean incompetant shooting.
You will note that the majority of thes occurances happen on weekdays when nobody is around. There is a reason for this, and it is because the individuals we are talking about know they are incompetant and are trying to avoid contact with those who are.
I am not a big "lets have some new laws" kind of guy, however when it comes to common military battle rifles, it would be nice if it was manditory that when you bought the gun you also bought a class to learn how to use it safely and efficiently. That class needs to be about 4 days long too,a s nobody is going to get this stuff in an afternoon!
I personally think that it is a good idea that you know how to run a gun if you are going to own that gun. Unfortunately many people don't give a ship about what I think, so they will never get trained beyond watching a video or playing video games. Real range time with real instructors is the only way to become competant with a complex weapon such as an AR 15 or any other battle rifle for that matter.
Fortunately since most people are not going to get competant instruction of using their guns, If I do have to go up against them, I can be pretty confident that I am better than they are. Now if I see SEALS or someother easily identifiable gunfighter type exiting the Black Suburban then I'm running the other direction!
Randy