The terminal velocity of something as small as a bullet (e.g., 38 special=158 grains) is not lethal.
However, when people randomly fire a bullet into the air they do not fire it directly perpendicular to the earth's surface. Especially not a bunch of drunken cubans and mexicans on New Year's. Such a random shot will be fired at an angle which makes the bullet lethal.
Mmmm, maybe I'm wrong, (I often am) but I thought that an object falling toward the earth through a vacuum would continue to accelerate until something acted on it to slow or stop it's rate of acceleration. In the earth's atmosphere that something would be the resistance of air to the object's passage through it. If I'm right (and I'm not claiming that I definitely am) an object that is dense and heavy relative to it's size, a lead bullet for instance, would accelerate to a higher velocity than would an object that is lighter in weight relative to it's size, a similar size piece of wood for example, before atmospheric resistance stopped it's acceleration. If I'm remembering high school physics classes correctly, that rate of acceleration in a vacuum is something like 64 feet per second per second, or thereabout.
Although you're no doubt right about the shooting skills, or lack thereof, of drunken holiday revelers, it seems logical to me that a bullet falling perpendicular to the earth's surface would reach a much higher terminal velocity than would, let's say a piece of styrofoam of the same size. That is of course an extreme example of what I'm trying to say, but IIRC (and I may not) either Galileo or da Vinci proved the validity of a similar theory by dropping a metal ball and a feather off the leaning tower of Pisa at the same time and observing which object hit the ground first.
In any case you seem to speak on the subject with a certain degree of authority, so I will defer to your knowledge of the matter until someone who seems to have even more knowledge on the subject posts a conflicting answer. There is no animosity on this end of the conversation, I'm always glad to learn something new. If it is true that is.
I'm so slow to comprehend technical stuff that it took a couple of read-throughs for me to get the gist of the article, but if I understood what it says it seems to confirm my ideas. Read it and see what you think.
In the interest of truth.