Not too difficult with a phone app.
Could you do it on your very first attempt?
Or, would it require some practice and experience?
As others have pointed out, not hard to do. targets all concentrated, no return fire, etc. Wouldn’t be hard at all.
I’m questioning whether his weaponry would’ve been up to it. Barrel overheating is a real factor, real fast, on rock and roll.
“Or, would it require some practice and experience?”
It would require no practice. But in the state of Nevada it would be incredibly easy to find a place to simulate that shooting area and practice. I could find a dozen spots with 5 miles of my house just by picking the right hill and watching where the dust kicked up from the shots.
But that is literally as easy as hitting the side of a barn from across the barnyard.
Not too difficult with a phone app.
spray and pray into an area where 22 thousand souls are packed shoulder to shoulder you’re going to hit something. At a quarter mile away even in a lit up area he wouldn’t be seeing individuals, just blobs of people. The muzzle flash at that high rate of fire would keep his ability to focus way off. Granted a trained auto rifleman would have inflicted more casualties, but 600 is a horribly high enough number. The scoped rifle would do him no good on auto or bump auto, only semi automatic.