Hello, I'm sorry to hear about Rocky's worms. You probably can't do much tonight as pet stores are closed.
The small white worms or "seeds" or "grains of rice that you are seeing are likely tapeworm egg packets. Tapeworms are picked up by eating fleas or rodents. They are not directly transmittable to other pets or people as they need an intermediate host.
If we don't stop the source he'll continue to get them. You may wish to use flea prevention like Advantage to make sure he doesn't bring home fleas and flea eggs if he goes outside. Unfortunately unless you keep him indoors you can't change the hunting part.
Treatment itself of tapeworms is fairly easy. Praziquantal (Droncit) is the preferred drug. You can get this from your veterinarian, possibly over the counter through a pet store.
If you aren't comfortable giving him a pill your veterinarian can give an injection of the medication.
Once he's treated for the tapeworms you may see many passed in the stool for the following 24 to 48 hours. Don't be alarmed, this is normal and they should be dead. Sometimes a bit of loose stool too just from the irritation of the worms dying and being passed.