Basically aimbots then?

I've played this game, some rainbow six IIRC, some people held hostages, wasn't even on hard btw., I come up from the side, actually a bit behind one of the terrorists, try to aim, bam, headshot at 30 meters or so, there wasn't even any real animation, he just instagibbed me from one moment to the next, I quit that game in frustration and haven't touched the singleplayer again.