What to do about increasingly hostile, violent, and dangerous teenage boy

(Posted in r/autism too) Boy, age 15,who has been diagnosed with PDD-NOS. Along with that, he has ADHD and intermittent explosive disorder. Has had maybe 3-4 total hospitalizations. He has been problematic ever since childhood, but now well into his teen years, he's created a very unsafe, dangerous environment in his family household. The family has resorted to hiding knives because on numerous occasions he has threatened to kill me or other family members. He has become aggressive with parents, even grappling with or kicking them and giving them scars. He screams abuses at his family, classmates, and teachers, throwing around the N-word and saying the most hurtful and offensive things possible. He idealizes homicide and talks about slitting throats or "having fun" with anyone who manages to tick him off (doesn't take much). No amount of kindness or patience is taken by him-- it is only met by grimaces, swear words, or middle fingers, making professionals, teachers, in-home therapists, or social workers not willing to work with him. He is arrogant and pompous and thinks himself reasonable and the voice of reason, but in reality his logic is flawed and his reasoning is absent. He offers his flawed, dare I say stupid, opinions when no one has asked, and even when he has no experience on matters. Opening curtains, or forgetting to turn off lights will without fail put him in a rampage. He doesn't respond to directions to even brush his mouth, shower, leave for school, and practically still shits his pants. He has a computer addiction, which has pervaded for years and has left him overweight, and spends his early mornings to late past midnight on the laptop. This is the only thing keeping him "sane" but basically non-functional. He enjoys watching ISIS beheading and torture videos, and has looked up how to make bombs. I do believe he knows he is in the wrong, as he at times recognizes his behavior is absolutely monstrous, yet he does nothing about it and cannot seem to change. The parent deals with boatload of health problems, on top of raising 4 kids alone on a poor salary and sending them through college. The parent does not need this additional load of stress. He has been kicked out of schools, and the school system has failed to help the parent properly place the boy somewhere where he can get the counseling and proper help he needs (preferably in a residential program so he is no longer a threat to his family). The family is at a loss for what to do next. The school system is failing the family and the boy, and the boy only seems to bring out the worst in everyone he encounters. What can be done for him and the family? Sorry for lengthy post!! via /r/Parenting http://ift.tt/2qtJZbX