My friend's account was hacked

My friend had his account hacked, they linked his account with another email that isn't his, but now he can't recover it, he spent years playing Apex Legends, he had inheritances, skins and everything else on his account and now he can't log in, so What can be done in this case?

His nickname is XxMazaCrazy, his original email is fer****@gmail.com 
now it is linked to the hacker's email which is ro*****@travisbezos.com