Imagine you live in a society that allows personal gun ownership. Obviously, in such a society you still don't want people running around shooting each other willy-nilly, so you make a law: shoot someone, go to jail.

Now imagine someone pulls out a gun and shoots you. Result: you're dead, they go to jail.

However, you'd really prefer not to be dead. So imagine that someone pulls out their gun to shoot you, but then you pull out your gun and shoot them. Result: they're dead, you go to jail. It's what the law says, after all.

This is undesirable to most people because it looks like you've been punished for defending yourself. So we'll change the law: if someone is pointing a gun at you, you can shoot them without going to jail.

Now imagine that someone pulls a gun on you, then you pull a gun to defend yourself, but then they shoot you anyway. Result: you're dead, and they don't go to jail. It's what the law says, after all: you were pointing a gun at them. Oops, it's equivalent to having no law at all! This is the worst form of the law so far, and it's also the same thing as the paradox of tolerance.

The way you solve this is the same way you solve the paradox of tolerance: you say that the initial aggressor does not receive any protections if their own weapons are used against them. This produces a result that matches people's intuitions. This also creates a lesser problem, where people try to toe the line of aggression and goad someone else into making the first move so that they can justly retaliate, but it's still a vast improvement on the situation that intuitively matches how people expect things to work, which just so happens to involve ethics that are conditional on the behavior of others. The condition in this example: violence is acceptable, if it's in self-defense.

EDIT: I see this is being downvoted, would anyone care to explain their reasoning?