You can either decrypt the pass with a click of a button or cant do it at all.
Hashes today are not a way to encrypt a password. not 1 hash anyway...
They probably did a md5/Sha1 with no salt and no rehashing - Idiots.
It was SHA-512 with individual salt.
Yeah sure it was

The hacker is either a psychic triple handed ninja king or you didn't protect the passwords.
One of them sounds better - but the other one is the logical choice.