The brief case is actually a ballistic shield, but it failed to operate as intended. it's supposed to open and unfold to three times longer, blocking Abe's silhouette. I would agree it doesn't look like a regular bullet hit, but also: it was a homemade gun using black powder, hence all the smoke. So the projectile doesn't quite have the same velocity or power as proper shot fired from proper gun (I guess?). Still could be fake though.