A fully automatic rifle is quite hard to use on full auto and accuracy suffers. If setup is done properly, they can be quite accurate.
In this instance, that is unlikely. It is just as unlikely that these were fully automatic rifles.
Yes, and from the looks of him he couldn’t cart all that weight with some help...esp. if he had 1000 rounds of ammo. Likely he had ARs (semi) and was out for vengeance of some sort or this was a false flag!
The M16 in rock-and-roll is a dedicated mountain climber.