Can someone help me help my father? Smoking in secrecy...?

Hi, I'm a 15 year old girl in desperate need of guidance. Here's the story: So ever since I can remember my father always said 'smoking ciggerets is bad', which they are. He even said that they should be illegal, which they should. One time though I asked him if he ever smoked, and he said 'oh well when I was young I did but I stopped as soon as I found out how bad they were' so for the longest time I was under the impression that he was totally out of the smoking loop. But recently I became suspicious. It all started when I noticed he come home smelling smokey from concerts, I brushed it of because, well it was a concert and lots of people smoke. But then one day he came home from a business trip reeking slightly of it... I asked him what it was from. He a bit too quickly responded with a 'oh just someone from work smoking around me...'. Also my suspicions grew when I got a shirt out of his dresser and he got mad at me an said never to look through his dresser, ever. You only tell someone that if your hiding something. And then recently we were on a family vacation and he would randomly be gone for a long time, which concerned me. And what put me in shock was one night he was snoring so I went to search through his things to find his extra earplugs, while instead I found a lighter. I tried not to panic, but I had to know the truth. I did come home eventually from the trip, with worrisome thoughts racking my mind. And one day I happened to be alone, when all the sudden I felt the urge to search. So I did, starting with the top drawer of his dresser... I pushed back the socks to see a small white box. A cigerette box. My heart stoped and I screamed and ran downstairs in tears. I have no idea who to talk to, my brother? My mom? His mom? I only saw one pack and hes never ussually absent so he probably doesnt smoke a lot... But any amount could kill him... I don't know if he's trying to stop, but please I dont want to lose him. Tell me what I should do, please...