Actually, a lot of them knew how to hold a gun correctly, and fire... they just weren't ready for the amount of recoil. That things packs a punch! I'm pretty sure I've seen one of those at the firing range before. At least, it looks like it anyhow.
.577 round. meant for one thing, and that is stopping what ever the crap is coming at you. (originaly designed for large game takedown) all you need to do is make sure you have aimed correctly before you get knocked on your ass.
P.S.
The last guy was the only one that had fired that weapon before. He knew that rifle.