Need Advice: I Got Angry at My Older Brother for Hurting Our Younger Brother

Assalamu Alaikum, brothers and sisters. I hope you can help me with something that's been troubling me. Our parents are elderly and busy, so they can't always pay close attention to my younger brothers. I'm currently in grad school, and the other day, my 13-year-old brother (let's call him L) and our 8-year-old brother (G) were in the living room. L was playing a phone game while G watched, which they usually enjoy together. Suddenly, when L's phone battery died, he went upstairs to charge it, with G following him. Out of nowhere, L put his hands around G's neck and squeezed him, making G tear up and hold his neck in pain. G was quiet, probably scared to cry out. I asked G what happened, and he said L choked him but didn't know why. I called L to ask why he did that, but he seemed indifferent and didn't seem to care. I was so upset that in anger I ended up hitting him, which I don’t like doing at all. I shouted at him, asking why he would hurt G like that, especially since G was just excited to be with his older brother. L said he was just trying to push G aside because he was in his way, but grabbing the neck and squeezing is way beyond that. This isn't the first time L has been rough with G, and I reminded him that as he's growing up, he should protect his little brother, not hurt him. L is a smart and funny boy, and I just don't understand why he would be so cruel to someone who looks up to him. Interestingly, earlier that day we were fine; I even took L out for some food and we had a good chat. Now, I feel conflicted because while I was trying to protect G, I also caused harm to L in my anger. When I think back, I feel a mix of sadness and frustration. I really need advice on how to handle this with patience and wisdom, so I can help both of my brothers grow with love and respect. Jazakum Allahu khairan for listening.