Ex bf sent threatening text message to me?

I accidentally rang one of my ex-bfs using my mobile phone number (it was a misdial). I've dialed his number accidentally before last year as well. We broke up 2 years ago. After I dialed his number by mistake, he sent me a text message saying "I know who u are and all my friends know what you are like. If u call me again like this I will refer you to the police". So I tried to call him again to apologise, but he won't answer his phone, so I sent several text messages telling him it was a mistake and that I am sorry this happened. I asked if he can forgive me and hoped he wasn't mad at me. But he didn't reply back. What's with his response to my misdial ? Why is he being so hostile and threatening? What else can I do in regards to this situation?