Is god willing to prevent evil, but not able?
Since some have a theory that this is the seventh day (still) and God then still is relaxing, it might not be a priority.
Is he able, but not willing?
I myself have a theory that God is not "preventing" evil, as first of all, it should be human that does that (by choosing the right), but besides that, it would go against the laws of nature. If God shows will and power to, say, kill a murderer before that murderer kills someone else. First of all, it would mingling with out free will, second it most likely would be an unnatural death and people would find it strange.
How would people not react if the ice on the North Pole stopped melting all by itself, without nothing else changed?
It is quite possible that God has to do nothing in order for nature to take its course. It might be something learned from back in time, where mingling with humans often ended up bad.
But of course, as many might say: God is nothing but a fragment of our imagination and thus are neither benevolent nor omnipotent.
On the other hand, many can say that the faith in God makes the believer be able to do many thing, and in the power of people willing to good, God is both omnipotent and benevolent; in the believers we trust.
There might be a reason for things happening.