Cats are very particular about their litter, preferring a certain texture, appearance and smell. Your little boy obviously liked the old litter and was flabbergasted when he stepped into the box to do his business and found out things were not as he expected.
The trust between litter box and cat was broken, and it will take some time to mend it. For heaven's sake don't make any other changes...he'll eventually learn to trust his litter again.
[
Collection
]
[
|
...
]