By aggressively i don’t mean physically aggressively, just very persistent. You text, he doesn’t reply, you then message on Facebook, he doesn’t reply, you are checking if he is online etc you then you text again etc, he doesn’t contact you on your birthday, you text telling him it’s your birthday (why?), when you see him at a gathering you followed him around the pub demanding to know what’s going on, he tries to leave, you insist he stays, he finally leaves, you follow him outside, he tells you to leave him alone, you don’t leave him alone. Thats very persistent way of pursuing someone. That’s why he mentioned involving police

I didn’t say anything different than others said on this thread. He demonstrated through his actions that he isn’t interested in romance of friendship, at this point pursuing him probably need to completely stop. You got to let him go