If your son is determined to commit suicide, nothing you say will change his mind. But you can have him committed by calling the police and telling them that he is a threat to himself or to others...they can hold him only 72 hours however.
I feel for you, but if you son does in fact do what he says he is going to do, you had nothing to do with it and you couldn't change his mind if you tried. Then again, he could be threatening as a device to get your attention, which many people do...This is merely my opinion and i am merely sharing with you what we did with my brother in the same situation....have him committed...his threats to kill himself if the police come may only be threats...but rest assured, if he wants to do it, he will do it regardless of whether or not you call the police.
Bless you and keep in touch.
I am now 24 years old, but in my teen years I was very suicidal. I was sixteen going on seventeen I believe. I don't know how old your son is but this is what happened with me. I had counceling that night and as I left I said good bye to my mother, I believed that was the last time I would see her for I had made plans to take my life. I told my counseler this and he notified my mother. She came down and tried to talk to me. I ran away from her and my counseler. The next day I was put in the psychiatric ward at a nearby hospital. I was sent home three days later even though I knew I wasn't ready. I ended up back in that hospital not even a week later. I had attempted suicide. My parents and I had just finished fighting and I couldn't take it anymore and I needed help, I didn't know how to tell them what was going on. I took some prescription pills my dad was taking, my sister found me and dragged me by the arm up to my parents. My dad and sister than drove me to the hospital. I didn't have a choice about going there, I really didn't like the fact that I had to be there a second time, I hated the first. I was upset that I was put back there. Now I look back and I realize that being forced there was the best thing for me at that time. I really didn't want to die, I just wanted help and was afraid to ask for it in addition to not knowing how to ask for help. If your son is under 17 you can have him taken to a psychiatric ward, he may not like it but it may be the safest and best place for him. If he is over 18, I believe you can call the police I am unsure about that. I hope everything will work out for the best and always let your son know that you love him regardless of whatever.
I will be praying for you and your son, If you need anything please go ahead and e-mail me, I will help you the best I can, for I know what if feels like to have a family member take there life, my cousin took his two years ago next month.