Hello Opppie, and a warm welcome.
Sophie_M has provided you with some links for you to browse over and many good points will be shown to you.
I am deeply sorry for the situation you are in because thoughts like this, although they may not be said by a person, doesn't stop them from thinking about it, especially when they are in a dark hole and can not see any light.
You can contact the police who may decide to take him to hospital for his own protection, this maybe enough to help get him over those deep dark thoughts he maybe having and be able to talk with someone who is qualified.
You could also contact Kids Helpline 1800 55 1800 by phone, webchat or online, they help people up to the age of 25 and can suddenly relate to anyone who is not feeling well.
Please remember that people in this situation always want to be alone, only because they just don't want to keep answering questions posed by their loved ones who are deeply concerned, but may not know why they feel like this, or simply are unable for the want of speaking.
You need to also look after yourself because as frightening as this is, you need to express how you feel starting with your doctor and please ask them about the mental health plan which entitles you to 10 Medicare paid sessions with perhaps more sessions available for yourself.
We hope to hear back from you when you ca.