OMG! I am sooo sorry!
When I was fourteen, I did the same thing. My dad caught us before I had taken any more than a sip (blecchh! It was sooo gross!), and he stayed completely calm... too calm. He told me to go to my room and wait. That was the most frightening ten minutes of my life! When he came up, he told me that he was disappointed in me, but that he understood how hard peer pressure could be. He said that the same thing had happened to my grandfather, but that he ended up dying of liver cancer forty years later. Then he said that he wanted me to decide for myself what kind of life I wanted to leave, but that he prayed that he would never have to bury his baby girl. Then he broke down and started crying.
I am not saying that this is the best method for you, but it sure worked for me. I think that it made me feel as though I still had some control over my life, like an adult (which is why I'd been drinking in the first place- to feel more grownup).