A pro hit wouldn't leave evidence everywhere, unless he doesn't exist in any database - DNA, fingerprint, biometric, etc. - which is very difficult to do. The news is even going so far as to claim he used a B&T VP9 (very rare) which would require a manual re-rack after every shot. Unless it was a sanitized version from a TLA, it's probably traceable. And not sure how they would be able to determine this within 48 hours. I'm guessing an undergassed gun without a block in it using subsonic ammo. Pro hitters don't inscribe messages on shell casings unless paid to do so.