Actually it's always happen when my girl go to school. This time she was hurnt by schoolmate and next she turned to the one who hit other child. I think this is normal as they are straight forward and not really good at speech so hit / hit back is the easy way for them to present their will.
When my girl came home and told me she was hit by other child, I always asked her why, cause for my experience sometimes may just because my girl wrong first.
But of couse I will teach her how to protect herself: Say "No" loudly to stop the child + ran away -> told the teacher
Mostly I'll take this chance to let her remember being hit/hurt are feeling so bad, hope she won't copy this act.