My brother has been having problems w his head

It scares him. He has the same repeated thoughts over and over. He obsesses over it and he just wants it gone. He's really starting to scare everyone because he's also making suicidal comments because of it and I don't know how to help him. He asked me if he should go to the hospital, and I said no, that he'd be safe with us, and I'm 100% sure of that, because he sleeps all night, and we're always with him during the day, so he can't hurt himself.
I'm just worried about my baby Jake.