Something may come of this, but for the most part I wouldn't be too worried - probably just a nobody with a sadistic streak. On the turnside that he does try to do it on something bigger, carry around a knife - sadistics get their pleasure out of torturing defenseless things - and the key word there is defenseless, so it'd be handy to keep some pepper spray and something sharp.
The pepper spray to get them down and the sharp thing to keep them down.
All the same, don't get too worried, notifying the authorities was the right thing to do - and I'd tell all your friends about it, so they could notify them too. the more reports, the bigger the problem.
But otherwise, there's not much you can do.