Whatever you do, do it nicely.................
This very situation happened to me and in fact , i would have to say this could have been written by him exactly to the word.......................... !!
But, he informed me that i wasnt "the one" and that it was my fault he was now so upset, because he had felt obliged to say yes to going out with me because i liked him....................................and really he hadnt wanted to !!!
( so why did he sleep with me i wondered ??)
I could accept me not being "the one" , but i couldnt accept that he had to be so bloody hurtful in the way he told me - and when he said he wanted to stay friends, i couldnt because a friend would have been more caring, more thoughtful and kind.
Good luck