Depends, like the type of nerve gas, depending on where it attacks the spine, it can cause hands to rigor/clench/etc or just go limp… For what it's worth, you can see the projectile being released by the person in the white t-shirt using VLC player. If you watch the video filmed from his left and zoom/crop before the moment of the shot, tap "E" and it will pause it on a single frame. Then tap "E", each tap will move one frame at a time and you can see the projectile as it passes in front of the guy in the black shirt. It looks like the projectile took a wicked curve due to the short barrel, slammed through his back/neck area, hit his bullet proof garment, deflected, and only because it grabbed his t-shirt can we see 'something' pull up at his shirt before, in my newly formed opinion after watching in slow motion, spins upward through his carotid artery then likely into his brain. The guy on the roof, may have been 'a' shooter but after careful review, he didn't kill Charlie.