Follow the link in my sig for an article on Avoiding New Tank Syndrome.
I agree that you should take fish back to the shop - they sold you far too many fish and angelfish need a deep tank anyway (20 inches ideally). It makes me angry that Local Fish Shops do this to newbies - it's ignorant and cruel.
Anyway, there's no point my ranting. Read my article and get that tank cycled, either using fishless cycling techniques or by an awful lot of hard work trying to keep some of the fish you have alive. The fish are possibly picking on each other because they don't have enough territory (in the wild, not being able to get a territory might mean you and your young starve, so its not a trivial thing to a fish) and also fish will tend to pick on any fish that is dying (presumably that fish is using up resources and would be best out of the way, as far as they are concerned).
Another little tip: always beware trendy names. It could mean the fish are dyed which is an incredibly cruel process, or the name is being used to cover up what exactly the fish is e.g. Chinese Algae Eaters, which are aggressive, large territorial fish being sold as "Golden Sucking Loaches" so people don't know what they're buying. Always check the species with the Scientific ( "Latin" ) name and make certain you're buying what you think you're buying.