Thank you all for the advice. I have a RR750xxl. All but 5% of the water was out of the tank when I got home. I used a shop vac and now I have a carpet blower running. From what I can deduce, a siphon started.
I may end up out of the hobby for a while after this one. The tank is to heavy to be taking down and putting back up again.
On a positive note all of my fish survived.