Mate I’m sorry to hear about this. Bullies are vile people. I was bullied throughout secondary school nonstop and has had an effect long term on my mental health.
you’ve done the right thing in getting it reported and telling him to report it if it happens straightaway. It’s good that’s he’s also able to tell you about it and be open as he can get the support that is needed from the family. This will give him a lot of reassurance and comfort when it’s needed.