Why my friend did like that? :(?

So, I thought he's my good friend because we always get on well together, He's the kind of guy who's very sociable with girls , unlike me ~ he knows that I'm not sociable but he said he will help me , so today, he met two new girls , he told me that he will introduce them to me , but he just went away with them quickly, I followed him and met them (of course I didn't talk much with them cause I'm shy) but later, I was walking with him and these girls called him so he went and left me ~ and also after I finished school, he was walking with them in front of me, saw me but didn't say anything about that nor talk with me ~
P. S: when I met these girls from him , he was speaking with them and didn't listen to me nor talked with me.

I'm so so angry on him now, why he act like this? I thought he's my good friend but he's not ~ because of some girls, he sold his friend... I feel really sad ~
Why my friend did like that? :(?
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