OP, it is fine to have him evaluated. There was a set of twin boys who were very much like you describe but on an increasing basis. It started around 3.5y and just kept escalating...the parents knew something was off and were taking them to be evaluated. There was an issue that was discovered with one twin and is being treated.

It doesn't sound like yours is this extreme but if you would like to check in and ask a professional it wouldn't be wrong.

Fwiw-Empathy (at least cognitively) and remorse are intrinsic, unless you have someone on the more extreme side of the psychopath spectrum. If he can and does show genuine remorse at other times, I would not be concerned about him having a deficit but certainly you want to reward kind behavior to his sibling and others.

Totally normal. My DS *raged* from ages 2-4, some months it was a daily, long, ordeal, sometimes months in-between. Never at school, but at home he would lose his mind over small stuff. He threw stuff, hit us and screamed until he couldn't. Now he's 5.5 and his last memorable freak out was over a year ago. During his episodes, we took him to his room and one of us stayed with him and made him stay there until he could calm down. We praised him for regaining composure, gave him extra love and braced for the next one.

Now that I'm further from it, I think he was reacting strongly to having a veryyyyy needy baby brother and losing attention from me. I took Dan Shapiro's class, you could buy his book, Parent Child Journey, and it really helped me see him more clearly.

sounds pretty normal. You can

practice managing frustration gracefully when the stakes are low (time to take a bath, we're all out of cookies, you lost the board game),

model how you are managing frustration: you can say out loud "I am so frustrated! My favorite sock has a hole in it/I got sent back to start in Candy Land/I dropped my last cracker and the dog ate it!" and then narrate "I am going to cut up my sock to use as a rag so I can still enjoy it/take three deep breaths and hope for a better draw on my test turn/eat some carrot sticks if I'm still hungry, then pet the dog"

praise a LOT when he handles something well. Notice what strategies he used and identify them for him. "You were so frustrated when your sister touched your blocks! I like how you got her a toy to keep her busy while you worked." "Thanks for being patient while I was on the phone with Grandma--drawing a picture while you waited for me was a good idea! I'm happy to help you blow up your beach ball now." "I know it was hard for you to stop playing and get dressed. I liked how you sang a song while you were doing it!"

do what helps with just about every 4yo behavior: make sure he gets a lot of time with you, time outside, physical activity, sleep, and healthy food and water. If he's not hungry, thirsty, bored, tired, or wiggly, it will be easier for him to behave. He's basically a two-legged puppy. He'll probably calm down a bit soon. When he's back with his friends, there will also be social pressure to act more reasonably and peer models of how to do it, and that will help.

Not a thing my dear. Your son is just going thru a developmental stage. Each stage at he moves toward maturity will be challenging. But it is very important that he receives the teaching, reinforcement, discipline and love that he needs at each stage. There are many good child development books out there. You might call this number-855 382 6433- and ask them to refer you to one that will suit your needs. I am praying for you and your family. You are right on track. Hang in there. God bless you and your family.