Autistic teen’s fantasy world mistaken for reality

My son (nearly 17) has autism and has been suffering depression. He’s now claiming that his depression was caused by “them” and that “they” want him to do something bad or kill himself. He tells me about aliens and pyramids etc. The thing is, I’m 100% that these are not genuine delusions, these are a fantasy creation that has got away from him and he truly believes they’re real. 
what do I do? He is so distressed. 

Parents
  • He appears torn between crying out for help and crying out to be left alone (because he believes a solution is impossible). His conspiratorial thinking - genuine or feigned - places himself either as special/chosen (this isn't vanity; instead, it's alerting to other people that he is in very real need of help) or else he finds it so daunting to speak of his self-harming tendencies that he's invented powerful outside forces to blame. In reality, he blames himself and feels guilty about this. Gentle navigation, by you, of this uncertain state of his is vital.

Reply
  • He appears torn between crying out for help and crying out to be left alone (because he believes a solution is impossible). His conspiratorial thinking - genuine or feigned - places himself either as special/chosen (this isn't vanity; instead, it's alerting to other people that he is in very real need of help) or else he finds it so daunting to speak of his self-harming tendencies that he's invented powerful outside forces to blame. In reality, he blames himself and feels guilty about this. Gentle navigation, by you, of this uncertain state of his is vital.

Children