See here for a more visible story about yet another attack by a man against a bunch of kids in China.
There is definitely copycat dynamics going on here, but it is important to keep in mind that the disease metaphor must be taken seriously. That is, not everyone catches a disease even if they are exposed to the virus. So, a few men have engaged in this bizarre behavior. The first event may have affected the others, but something else also matters--whatever it is that made these three guys imitate the first. Otherwise, this, like all phenomena that can be copied, would be far more widespread.
This is what separates this kind of stuff from a Zombie outbreak, where all those who are bitten would then become Zombies. I raise Zombies not to be too silly, but to point to the extreme end of the virulence spectrum (fictional or not). It is likely that much will be made of the copying, which might end up distracting ourselves from thinking about what it was that caused these guys to imitate and others not to do so.
Insanity and inequality are mentioned in this piece, but not bare branches.