I found this question on Quora: https://www.quora.com/Can-you-theoretically-shoot-an-atom-fast-enough-to-kill-its-target
I think the Quora answer is good but incomplete, and it got me wondering what would actually happen.
In theory, a nearly infinite amount of energy could be imparted into a molecule as you keep adding 9's after the decimal point, but lets put a limit on it, say oh my god particle velocity, but a much heavier object, like a gold atom, not a proton. (oh my god particle has roughly the energy of a baseball, 5 OZ at 94 mph, so an atomic mass of 197 means equivalent energy of a 61 lb object traveling at 94 mph - more than enough to knock an average person off their feet pretty easily.
Shooting someone at point-blank range, the atom hits them directly at very high velocity, would the atom pass through them leaving a slightly larger than atom size hole or would it interact with the atoms it hits to the extent where most of the energy would radiate throughout the body.
Shooting them from a distance where the atom would interact with air molecules and in the process, sending radiation in all directions, perhaps doing almost as much damage to the person holding the gun than the target, a little bit like the relativistic baseball, only much smaller.
I know about Anatoli Petrovich Bugorski and I think that stream of particles passed through him, and obviously didn't kill him. So, I'm thinking, the atom would pass through the person and not kill them, but I'm mostly guessing.