How to stop an under age tobacco user?

I'm saying A for safety and their privacy. Gender will not be told. A turned 12 just a few days ago and idk how long they've been doing it but it breaks me. Their one of my best friends and it kills me inside. (how I figured out:) I was at their B-day party and I saw a tobacco can. I thought to myself, "their mom and dad don't do it?" So I called A over and she said it was theirs. I just stared at A shocked and A said it tasted like beef jerky...I asked A how they got it and they said, "even if you are underage you can get it at -store name- easly." any way, my other friend and I tried talking A out of it by listing the dangers but all A said was "whatever." we tried to ease A out of it by joking around. didn't work. so we got serious. I said "some day, A, you're gonna die. If you die from this crap don't expect me to cry over your grave. expect me to say, 'You should've listened.'" then my friend said that they would tell A's parents. I'm scared for A and I'm scared to get parents involved. Please help. For my friend.