GM hacked?

Before we can answer that, let's ask;

Is there any reason that a GM would put their information up there? Given Nexon's apparent recent stressing of account security, it's safe to say that's a no. Ergo, the account was most likely compromised before the info went up, not the other way around.

Or it's some guy that's dissatisfied with his career and wanted to go out with a bang.

Something this big would be a perfect "fuck you" to your boss.