My bf wants to kill himself! Idk what to do?

I was sleeping over at my bf's house when his sister came up to me and said he's been talking about suicide, she then asked if I could talk to him. Idk what to say.... Idk how to even start. Btw I see him everyday. People said I should get invoked with him ually. Well we do have s3x. Other people said to get a bottle of wine. Well we r 15. Pllzzz answer cause I dont want to see him hurt. Ps we've been dating for 2 years