Assuming the casino had a basic firewall for outside of the hotel access, I am thinking the accomplice may have been in a room in the hotel.
If that were the case... How could they not have a separate firewall to protect the CCTV feeds? It would seem to me the CCTV should have stand-alone servers and a stand-alone firewall.
That being said, I would like to meet the intruder. I have a business proposition for him :-)