The shooting spot was about 250 yards away. That's WWII sniping range, but not particularly far for modern precision rifles. According to Ryan Cleckner (US Army Ranger sniper), precision marksman training in the Army makes you use iron sights out to 600 yards. A good setup these days can hit a dinner plate (read: a human head) at 1000 yards, and that's not even pushing it.

They didn't have to hit him the neck. They just needed to hit the general head area. They got lucky hitting the artery dead on, but any head hit has a very high probability of death.

There are millions of bench rest shooters with a bolt action rifle who could make that shot.