What would you do in this situation?

Storytime at library

My 3.5 year old has the idea that it is “play” time. He talks, interrupts, makes noises, wiggles, walks around the area, touches and talks to other kids. I have tried to correct this behavior multiple times. He says he saw other boys behaving this way the first time and thinks it’s ok. Well it’s not ok. Not with me, not with the other parents and not even with the other kids. We spent 2 weeks talking about the rules of the library. Be quiet, sit still, listen to stories, no walking around, no touching other people. Well he recited the rules all the way up until story time started and all went out the window. I threatened him to leave and he would correct for a minute. Well, we eventually did leave without much argument. But I was so mad, crying kind of mad. I am so upset with him. Mostly because he doesn’t behave this way anywhere else. What would you do? What should I have done? What should I do moving forward? Clearly I can’t just forbid the library because he clearly needs to get over this (I would have hoped already). Tell me your ideas and suggestions. Be harsh if need be. I don’t need it sugarcoated. I want this fixed now. What am I missing?