<human>: Can you summarize the given text in a few sentences?

I (23F) ended things with someone (27M) that I had been casually seeing for a few months. It was nothing serious. When I had the conversation about ending things with him, he freaked out and smashed my phone, tried to block me from leaving his place, and sent me a string of texts calling me stupid, a slut, etc. He sent me a text about 1 month later asking "What's up?" as if nothing had happened (I ignored this), and other than that we haven't really spoken since. I have no intention of ever getting back together. 

I know him through a close mutual friend, and I still hang out with this friend. I know that at some point I will end up in a situation where we both happen to be at the same event, because I hang out with this mutual friend a lot. I have no idea how to act towards him. Do I completely ignore him? Am I supposed to be nice to him and make small talk?

How do you guys handle the awkwardness of running into an ex after things ended pretty badly?
<bot>: Short relationship ended poorly and I'm pretty certain I will run into ex again, but don't know how to handle the situation.