On this case the person's problem is law enforcement. Basically they just need to pass off details to the FBI / local police and have the ex-admin arrested and put on trial. What he did was a crime

If a company walks away from this and doesn't take legal action; they should themselves get sued by their customers.

Destroying company property is a crime; wether it's defacing a website or ... it's not your property; you are just hired to maintain it (in one shape or another)