So this is a outlier only in that someone was equipped and trained to a fairly serious degree. Someone on the order of a squad designated marksman (SDM) is certainly capable of this. The US military has a few thousand active duty personal trained to that level across the several branches, and there are 10's of thousands of veterans. There are also many SWAT and other LEOs and an uncountable number of enthusiasts and serious hunters with sufficient training and weapons.
No serious training or equipment would be required for this close of a shot. I've taken deer over 200 yards away with my $500 rifle, no training other than shooting on and off since I was a kid.
I've killed deer beyond 200 yards sitting on a stump with a cheap rifle, it's not actually that hard if you've shot a bit before. The nerves though... you're right there, I couldn't imagine.