No closer to the assailant or his motive:
http://www.gambling911.com/Puerto-Rico-Adam-Anhang.html
Since this was clearly a hit, and not a robbery that went out of control, the motives are intriguing - particularly considering he was such an upstanding fellow. His friends / associates can't pinpoint any area in which he had enemies, and it's hardly information they'd have any reason to withhold.