It should be noted that these are not single shot kills. The 2002 shots are confirmed as multiple shots once the range was established.
The feat is still very impressive, especially since the equipment must have been custom modified in order to even point the weapon with any controllability. (roughly 80mils of superelevation, hold over etc needed to account for drop over the time of flight). This is significantly more (double ish) than the stock rail and sight would permit even with the lowest zoom setting. With the higher zoom needed to give a reasonable chance of pointing accurately the required increase is an additional 19mils (27 mils at lowest zoom, ~8 mils at highest zoom)