Weird Symbol Above Head

Okay, so I was hunting today and noticed that sometimes a strange red cross symbol appears over my head. (I dubbed it the "sharpshooter symbol"). I'm not sure if this existed previously and I just missed it for all this time, or if it's new. Either way, I have no idea what it means. Does anyone know anything about it?

This is what it looks like:

 Spoiler

EDIT: I noticed that whenever the symbol appears, it also appears on one of the monsters I'm attacking, which dies instantly.

Arcane Aim?

Arcane Aim?

Maybe, but the buff appears a lot more often than the symbol does, so I'm sorta doubting it.

Arcane Aim.... .__.

Doesn't Storm Magic or whatever have a chance of instantly killing a monster? The effect is kinda like what happens when Mortal Blow instantly kills a monster.

Arcane Aim.... .__.

Doesn't have an animation, at least for F/Ps. iAmFear's guess sounds likely.
Edit; And he's correct. http://www.southperry.net/showthread.php?t=42493

yeah.. Arcane Aim doesn't have an animation lol

That's the activation animation of Storm Magic - the instant kill part that is. Same as Mortal blow for archers- just colored red for i/L.

You sillies, he dubbed it sharpshooter and you associate wih arcane aim.

Oh, Storm Magic. That makes sense. Wow I'm dumb. LOL Thanks for the replies guys.

So was it something new, or did I just not notice it all this time?

I knew what the animation was supposed to look like for a while but had never seen it on my i/L- my guess is that they must have fixed it recently so now it actually displays the animation.