Well that was just hitting them, the needles might not have gone in. For an assassination where you specifically and visibly shove needles into someone for a guaranteed kill, I'd think the needles would go in, especially with the descriptions I've seen. I think at least the ends of the needles would break, which might affect how they move and how much ammo is needed for a kill, but then that should apply to just hitting things with that side too.

: I think you are over thinking that. It's cool for the sake of cool dude.

Well my guess is this why it hasn't been done already. Anyway I still don't see anything addressing what would/should happen if you're out of ammo.