Please, critters don't get "mad" and do these things. They do however get anxious when something has upset them and will defecate or urinate in places where "we" think are inappropriate. As said already, young or new cats will try somewhere else if the litter pans are already in use by more dominant cats. If you think about this you will realize that in nature, when given a choice, cats don't use a common toilet like we do. They seek out different places to themselves. It's not an easy thing for cats to adapt to litter pans. Amazing that they do as well as they do! Also, many people let the kitties have the run of the house without establishing a certain, restricted area with the litter pan in it to form the habit as already mentioned. So, give this youngster an area of its own until it's firmly established in the household and not intimidated by the other cats. Those of us who have bred and raised cats have found that it is a good practice to have at least one more litter box than you have cats on each floor of the house. So, if you have three cats.... have four litter boxes on each floor of the home. Something else that should be mentioned is, cats are usually fastidious by nature and many just won't use a fouled litter pan. More frequent cleaning may be needed. Twice a day is minimum for success. Any less and you will experience problems depending on the cats. Don't forget also, if you are having problems, to try different litter. Cats aren't that much different than us in that some just don't like certain odors and will not use a particular brand.
Good luck with the kitty, and absolutely get it neutered! LQ