If he's building plans that deep to steal from people. he's not just a thief... he's a criminal.
I don't think it was planned, actually. I think he was just planning to take all the money and run, but when he noticed people weren't going to just let him run off and were talking about contacting the FBI and were starting to collect bounties, etc etc, he got scared and decided to take half of the money (maybe the rest is already sold?) and give it back, hoping that would save him while still getting away with a fortune.
It seems pretty convenient that it's almost exactly half of the money that's gone. I also find it hard to believe for that much money to simply "trickle away".
That said, no one can be certain whether "Tom Williams" is lying or telling the truth. Yet. But I think this smells way too fishy. You'd think he would have at least posted something here on the forum when he took the site down if his claims were indeed true.
