I turned him down, now I got people threatening me?

So I turned a guy down, whos liked me for a very long while... He has already asked me out 3 times, everytime I've said no. The first time I told him because I didn't like him, and then he kept asking, and I didn't want to ruin our friendship, so I just told him I liked him to, but did NOT want a relationship right now. The other night, he had his best friend texting me telling me that I should go out with him, and she wouldnt stop... She did it the next day to, and I told her finally that i'd just go out with him. So He asked me out again today, and I said no, because I won't be in town all summer anyways, so we'd never see eachother. Now, his friend (who is a girl), is texting me, threatening to beat my ***, tellin me to go back to Russia, i'm a pathelogical liar, I play with guys hearts, and i'm a tramp. I dated this guys other friend (before I knew he liked me), then ended in a bad relationship. When my ex found out that he liked me, they broke up as friends. I told them to leave eachother alone, and they were fighting over me... I feel really bad. I'm being threatened. I'm 16. He's 15, and so is his friend. I don't know what to do, i've been really nice to him, because hes a good friend. But I feel NOTHING for him... In fact when I think about us dating, my stomach achs because hes NOT my type... Now they all hate me, and are making other people hate me to. What do I do?!