Is my friend really joking with me or is he just being toxic?

I am really confused with this guy who is(or was) my close friend in a class where i go these days. I am 23 and he is also 23 and we were really good friends and i used to share everything with him and he was nice to me too and as I am shy and introvert, he used to motivate me to talk more. But suddenly since Monday, he has been being different to me. Previous week he didnt come for any of the classes and lied to me that he was leaving the institute. But he came again for the classes from Monday which was 2 days ago but whenever I try to talk to him, he is saying "who are you dude?" and asked my other friend too saying "who is this guy? I dont know him?" Even on Saturday, we had a normal whatsapp chat but suddenly he is being this way. He is talking normally with everyone but is ignoring me and pretending that I am a full stranger to him. My other friend said me to just chill and said he must be joking but its been 2 days and he is completely ignoring me as if i dont even exist. I am wondering why he is doing that. Idk whether its because i act silly for my age and he used to get annoyed by me but other than that there is no reason at all for ignoring me and treating me like a stranger. Is he just joking or is he being toxic to me? I am an introvert anyways who has a harder time making friends whereas he has many friends.