I used to work for PetSmart. It depends on the quality of the PetCare manager and the people they hire as a staff.
I wouldn't blame it on PetSmart. I would blame it on Oscars aggresiveness.
What IS Petsmarts fault is they only allow you to order fish in increments of 12 (most of the time), which means you will stuff 12 tiger oscars in one cubicle. PetSmart also only allows a 29g hospital tank, which was probably full.
When I worked for PetSmart, our Oscars would constantly chew on each other, and beat the crap out of each other in that tiny cubicle. No matter what I did to resolve the problem, it was an on-going battle. I could only hospitalize so many Oscars in a 29g tank. Blame the natural aggression of the fish, more than PetSmart. Although they could of 'given up' at the point in which you saw these oscars, There is not much they can do to prevent such things from happening.
The same thing would happen with ANY other South American Cichlids, especially Texans.
Sorry to dig up an old thread, but I had to comment..