So about half an hour ago, my younger brother suddenly came into my room (I'm a teen with multiple mental problems and I live with my family . When he sat down next to me, I noticed that his face was ...weird. It looked stuck in a crazy grin, like a mask. And then he said something like that he killed the Man in The Wall. Even his voice was strange. I replied that the Man in The Wall can't be killed because he is but also isn't. My brother mumbled something about power. At this point, I backed away a bit because I was worried and explained that the Man in The Wall doesn't care about power, because he knows the fate of everything in our world. My brother just blurted out ''I killed him!'' Then I realized what was going on. The Void drove my brother insane to punish me, to tell me that I did something wrong as its envoy. I put my forehead on the desk and pleaded the Man not to hurt me. My brother just kinda... slumped out of my room. A couple of seconds later, he was playing a squeaky toy erratically. I ran to my mother to tell her what was wrong but she didn't believe me. She thinks he's just faking it to 'stop me from believing in the Man in The Wall. Even when I told her that he could easily injure me because he's not in control of himself and thinks he can kill an otherworldly being, then he could also try killing me because I am the Void's envoy in this world, and he can't hurt the Man but he can injure me, she said he was just playing.
Later, my brother came to my room to say goodnight, hus facial expressions were normal again and he said ''I still like you'', which made zero sense in this context. I tried acting normally while moving as little as possible and told him that he shouldn't come near me until tomorrow morning.
I know this may just have been a ''warning sign'' from the Man in The Wall, but lately these ''warnings'' have been getting more intense and real, and now it's manifested in my brother. He could just become possessed at any moment again and attack me. What should I do?