[Svartalfiar]

A .22 LR is lethal out to 700 yds, but I’m guessing he used an AR type rifle 5.56 / .223.

I'm guessing your guess is correct, but lethality is not practical. At 200 yd, a .22lr has over 30" of drop, not something many shooters can simply deal with. At 700? I don't see quick ballistics data there, but 500 yd is 35 to 45 FEET of drop...

[Eagles6]

A .22 lr wouldn’t be practical at 700 yds, of course, but is far more lethal than some think.
Have seen videos of shooters hitting targets at that range.
It was an AR, as I thought.