It is quite shocking and impractical for a hacker to return that big of an amount. There must be a very very very good or life threatening reason for him to do that. I mean, why go through all the troubles of stealing this amount and then just suddenly return it? It just doesn't make sense! Unless this person is already rich and would just like to make a point that it is possible to steal people's money/alts/coins in this system. If this news is true, then he had certainly made his point.