I don't know how to handle this case, I have two junior brothers in my small town who lives opposite to my house, one help the other to create a trust wallet and 100$ worth of Ethereum was deposited into the wallet, two days later the fund was moved out to am unknown address, after asking few questions from the wallet owner I found out that the other guy has access to the wallet too,
Then you have the criminal, am not going to beat about the bush or try to paint words with evidence nonsense, as long as the real owner of the wallet said he didn't share his seed or private keys with anyone else, then the friend or brother who created the wallet is the thief, he should be held responsible, he took advantage of his friend's naivety and lack of knowledge of how cryptocurrency transactions work, to scam him.
I believe he did the dirty trick because he never warned the wallet owner to never share his recovery seed with anyone..if you are in my shoe what will you do..
You are absolutely correct, there is no two ways about the matter, he should be held responsible.