Hey guys. I've been playing Conviction for a couple of days now, and for the most part enjoying my time with it. I've gotten all the Vanish and Prepare & Execute Challenges, and I'm relentlessly close to finishing the Splinter Cell Challenges as well. However, this pesky challenge that I mentioned in the title of this thread is escaping me for some odd reason. I've successfully performed the action the challenge requires me [shoot camera -> guard goes near camera -> shoot guard in head/CQC guard] to do numerous times on both the single player campaign[on Third Echelon HQ after the garage sequence] and in the Infiltration Mode. But for some reason, it doesn't want to give it to me. I was hoping any of you could point me in the right direction? Much appreciated.

You have to wait a bit before you kill them. Other than that I don't know why.

I have that challenge done, and Ive never shot a camera (I didn't think you actually could). I think you have to run in front of a functioning camera so it sees you. When you run away, you leave your last known position. When a guard is walking up to the ghost image, kill him.
 
I actually got this by accident, so I'm guessing this is the process.

I got it by accident, in Thrid Echelon HQ, I tried to shoot a guy's head, but he moved and I hit the camera behind him instead. He started walking towards me, so I shot him and I got the challenge done some how. I won't argue with it though.