Posts from I urgently need some advice!

Guys, I need your help! I need some advice.
Okay, let me start from the beginning.

Recently, two jerks stole my friend Sanya's phone,
and started demanding money for it (1500 rubles). Sanya asked another friend of ours, Denis, to sort this out.
And Denis somehow met one of those guys who stole the phone; he was hanging out with his friends.
Denis approached them and told them to return the phone, but the guy told him to get lost... In response, Denis punched Pasha (that's the guy's name) in the face.
His friends jumped on Denis and beat him up...
Just yesterday, they called Denis's girlfriend and threatened her... Tanya (that's the girlfriend's name) told Denis that they wouldn't be together anymore, and he asked her who threatened her, but she won't say...
And now Denis is saying, "I don't care anymore, I'll kill that jerk, and then I'll hang myself; I have nothing to lose..."

Please, tell me what I should do? How can I talk him out of it? I've tried everything, but nothing works.

And is Denis the same age as him? If not, let him just forget about it. If yes, suggest that they "explain" to Pasha together what exactly he is doing wrong. Also, get Sanya involved, since it all started with him. Then it will be that Pasha and his friends are not against Denis alone, but against a group of friends. This will be the best solution, in my opinion, because at that age, people don't know how to "just forget about it," and besides, they are guys, and they need to defend their right to their place in the sun.

Is Denis your age?

He's a year younger than me.

He's the same age.