How can i help my brother im scared?

You have two problems. Your welfare and his. Maybe he has a serious illness. I don't know your family so I apologize for this next question - does he use drugs? Your concern for him isn't enough to get him to a doctor, which he desperately needs. But if you begin to feel even the slightest in danger, don't be afraid to call the police. Or if you live in an area where that might get you in trouble, arrange to meet a police officer somewhere out of sight of your neighborhood and then explain the situation. Show your brother love the whole way through and don't give up on him. Call 911 and tell them you have a psychiatric emergency.