At my wits end !!!!

Hi all please please please help I need advice .I have a 4 nearly 5 year old son who was diagnosed in the summer with autism,which was no real surprise.

His behaviour is totally out of control literally from the moment he gets up until he goes to bed he' disruptive and distructive...atm his fascination is with my dad and cat he chases them hurts them and provoke my dog until he gets a growing reaction and he just loves it and he just won' stop it' almost like he' enjoying it !!! Once I have taken the anmals out of the equation he will do other stuff he should I've tried distraction methods which works for a few minutes it' just awful ....I wonder if anyone has any Advice he hates being told no this often makes him worse and triggers a melt down any Advice greatly appreciated