He was dumped in a tank!
Here is what I was told about him when I inquired on Facebook:
Hey Jennifer! Hardy hasn't been heartworm tested yet and he weighs approx 50 lbs. We're going to be at the Walgreens in Seagoville tomorrow (Sat) for an adoption fair from 10 am-3 pm. You should come out, meet him and spend some time with h…im. He'll be at the shelter and we'll be set up on the right just before you get to the shelter. Come by and see us and we'll take you down there! We'd love to see him saved! Monday is getting so close and time is literally running out for this poor boy.
Here is his Petfinder page: