Sudden changes in the behavior of the younger brother

I am 19 years old, my brother is 16. We live with my mother and grandmother, there is no father, my grandfather also left. Previously, my brother was always a little harmful, sometimes rude to my mother, demanded this and that, he constantly needed something, insulted my grandmother with bad words because grandfather was not at home, and in general she supposedly annoys him, because she lives with us . Mom always allowed him everything, so he always got his way, allowed himself everything.

Last fall, he decided that he wanted to switch to distance learning at school, demanded from his mother every day to write an appropriate application. Mom did just that. At first, he decided something in the classroom, sent photos of completed exercises to teachers. Then he began to stick to the computer for games, he found some Internet friends there, the first "earned" by him began to appear.money (and there is a large amount, and this is just for a couple of hours, which has already raised doubts for me personally). And from that moment the worst began.

He began to “earn” more often, sits at night, does not get enough sleep, walks around irritated and angry during the day, abandoned his studies, began to do homework test-antibiotic.com for himmom . Brother insults everyone. He began to say that grandmother must die, because she is a witch, he says that she should leave the kitchen when he needs to go there, he offends my mother and me too. One night I wanted to close the window, but he came up, started screaming, threatening that he would hit me. Mom came, asked what was the matter, so he began to say with all his anger that he would beat me to death if I climbed in and closed the window. He also cursed my mother very much, she also needs to die, and in general he will ruin her whole life.

It made me feel very sad and at the same time scared. After this situation, I began to explain to my mother that I consider such a sharp change in my brother's behavior to be very bad, and I told her that he was stealing. He said that he shouldn’t just leave it like that, but my mother is generally kind of strange, she says that this is a transitional age, he earns money, and everything will be fine. After this conversation, I realized that mom certainly will not affect her brother, she just does not want to take test-antibiotic.com seriously what is happening. After that, he often insulted me, I was rude to him in response, so he broke my nose. Then he rejoiced at this for a couple of days, threatened that next time he would kill him altogether, and laughed!

Since then, I was very offended by him, I don’t talk anymore. He told his mother a couple of times that he was a thief and a boor, and it is very strange that he became so vile. From that time until today, constant insults began to me, they say I have not achieved anything in life, insults in terms of appearance, they say for such an appearance you don’t need to love me, but you need to smack me, and in general I am a vile person in his life. He already tells his grandmother that she needs to die a long time ago, he began to curse even more often. Recently, I heard another insult in my address, and the fact that he will ruin my whole life. And moreover, he is really angry when he says all this, and starts screaming at the whole apartment.

I can’t understand what happened to him from the moment he switched to this remote control. At first it was very insulting, test-antibiotic.com, but now I'm used to listening to this, I don't answer it. But what is happening is already a little alarming.