Fox says he was beset by financial problems. Perhaps he was going to commit suicide and then decided to back out. Since such a small amount is deadly, perhaps he suffered an accidental dosing.
According to most reports, there was enough ricin in that hotel room to kill hundreds, if not thousands of people.
Three vials of the stuff were removed, I believe.
I bet he was going to try a little extortion on a casino but didn’t have enough skill to carry it off.