[NaS]

I think it's not possible, since we don't have up-to-date info about the camera vector while the player is shooting.
If there would be a camera vector with every shot, it would be possible to calculate if the shot is straight on the line, but we can't since the camera vector doesnt get updated often enough.

At least that's the only way I can think of detecting this.

It could be done if the player does not move at all (no cam & no character movement) while shooting, but that's very unlikely.