Establishing Time-out

I have a 20 month old and a 2 month old. Both boys. My elder son is very... how shall I say; wild. He’s active, and loud and excited about everything. And- very protective over his younger brother.

Today while I was taking out the clothes for both of them- I was literally 6 ft. Away from my youngest, my older one runs out of the room, comes back a with a hairbrush (I have no idea he’s even back in the room, that’s how fast and quiet he was) and- well. He hit his brother on the head w the brush.

It was pretty bad cuz my baby was crying and tearing up and he has a small scratch on his forehead.

My toddler didn’t understand what he did, and in the heat of the moment, I run to my infant, held him and moved him from his brother.

As calmly as I could- I told him he hit his baby brother, it was a bad thing he did, and so he’s going to sit 2 minutes in time out on the rug in our room. (something we’ve never done).

He did it.

He sat quietly without moving or making a noise. He was whiny, cuz he wanted my attention- which I wouldn’t give.

But after the two minutes, he just got back to running and screaming and trying to kiss his brother, and I just feel like he’s still too small to understand the action and consequence of what he did.

I want a way to discipline him. No hitting- obviously.

But a time out kind of thing.

Any advice.

Btw- baby is fine, for anyone worried lol he’s a strong one (pic of both below.)