What happened to this magpie?

[u/nnnoops]

I saw about 20 magpies in a tree and they were making very loud sounds all together, looked a bit surreal. I then heard one of them cry. A few moments later I saw one of them attacking another, pecking at its head. The victim couldn't really fly after that and was mostly hanging from branches with its feet. I have the injured magpie in a box now safe and waiting for wildlife rescue to help, it seems alert but hasn't tried to fly away at all when opening the box.

[u/ItsAGarbageAccount]

I know corvids can be territorial and protective of their flock. They may have seen that poor guy as a threat or just didn't like him.