Did you get 945 gallons via Rachio interface or your water meter? Does Rachio show any sign of having been on today?
How did your landscaper shut off the water flow? Was it done via Rachio or via a water valve?
In my experience when system starts to water uncontrollably, like yours, it usually an indication of a something being wrong with a valve (such as debris clogging up the works). Hope you can get to the bottom of what ever is wrong.
You can find how to contact support here (link), but please keep us (community) appraised on any progress.