What should I do or how do I handle this?

Okay this is the deal I just got out of a relationship about a month ago that i was in for like 2 years (a little over) but I met this guy (well I had known him for like 3 years but just never knew him outside of work)He was a cop and came into where I worked for reports and stuff.Well anyway he asked me out and so I went and we got along great until...one day he had asked me to come over but I already had plans to go out with the girls(which I hadnt done in those 2 yrs I was involved)so I told him I couldnt until the following day.He made the comment well ifyou dont you're gonna see a side of me you're not gonna like.It kinda freaked me out.I told him to leave me alone.Hes apologized and gives me the sad story and all but I still cant help but feel like this was a threat.Now he's trying to say I probably hooked up with my ex which I did not do and he knows that.Anyway what should I do?He's been so nice since we started talkin other than this.I just felt uncomfortable.Am I overreacting