How do I maturely handle harassment from an ex-boyfriend?

I'm letting a friend of mine stay over at my flat because his flat is being fixed up. I was spring-cleaning in the middle of winter and came across my ex-boyfriends' engineering equipment. It's quite expensive so I figured I would inform him of its whereabouts so that he can come pick it up. Now that I think about it - I could have saved myself the drama and just sent it through the post. He said he would come pick it up this week but since he lives far away he would have to stay over at my flat for a night. I called 2 days ago to confirm a date for this week and he said he wouldn't be able to come due to transport issues. I brushed it off and mentioned that it was probably for the best since my flat is kind of crowded with my friend staying over and all. Ever since I uttered that sentence my ex has been harassing me through the phone. He asks me tons of questions regarding my friend and if I don't reply immediately he starts throwing a tantrum and mentions all my personal flaws. I feel kind of bad because I feel like this was somehow my own fault but I don't know why my ex is acting like this since he hasn't spoken to me in +/- 1 year. I broke up with him about 4 years ago and it was a good break-up. We remained friends for a year before gradually decreasing our social interaction with each other. I've given up trying to calm him down at this point. I don't think the messages are serious enough to file a police report but they are rather... difficult to comprehend. I considered blocking him but I still need to find out his address and mail his equipment to him. How do I maturely handle the situation?
How do I maturely handle harassment from an ex-boyfriend?
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