There are numerous clay games, each with it's peculiarities. There's:
- Sporting clays
- ATA trap
- Skeet
- 5-stand
- International trap
to name a few. The gun that works best for each sport is a matter of personal preference and the specific demands of the sport. No one make/model can do all of them well.
My guess is that your son was probably observing a game of ATA trap or Skeet. I would recommend that your son find out what game is played at the local range, or wherever he'll be shooting. Then we can talk about what action type he should be considering.
Other things we need to know are whether or not there are already shotguns in the family that he could borrow and use. For example, even a single shot (choked in anything except cylinder choke) would be sufficient to practice single-shot trap with some friends. It would be useless in doubles, but any double, pump, or semi would do fine for getting started. Skeet requires 2-shot capability and open chokes.
Also, if he wants to compete in local shoots and further afield later on, he'll want a gun specialized to the particular game. And, he'll very quickly outgrow anything that $500 can buy.
ETA: Stoeger Condor swings like a 2 x 4.