My reloading mentor suggested putting a drop or two of oil into the case, onto the "inside" of the primer, which deactivates it. I have had a few cases where I just deprimed it as normal, but very carefully. I figure if the case is empty, if the primer does go off while depriming, it'll make a big noise and force the primer out of the case.
As for the unfired rounds, go ahead and disassemble it and recycle the case and head. I'd toss the powder; you have your own new powder and recipe and you don't know what kind of powder is in the case.
It's curious that there would be empty cases with unfired primers out on the range. Could someone have started to reload them, decided the cases were bad for some reason, and discarded them?
alpo, you beat me to it while I was typing. Glad we agree. It means I got something right.