Big brother behaviour

Recently just welcomed our second son 3 weeks ago. For a little while before his birth and since his birth our 4 year old sons behaviour is getting worse.
He was a sweet little boy who at times was naughty but generally a very good behaving boy.
Now he yells and throws tantrums, doesnt listen to anything we say, punches and throws things and has started hurting our pets.
His rountine is a bit all over the place with baby being born at the start of school holidays and three weeks of public holidays on kindy days, so hoping behaviour improves when routine normalises. He has also recently dropped his day time nap. His dad is still off work for another week and spends most of the day playing with him or holding baby so i can play with him. We are trying to make sure he still gets attention from both of us and involve him in the care of his baby bro.
I knew having a another baby might disrupt life a little bit didnt think it would turn my little buddy into a devil.
Any suggustions to help him through this rough patch?