Any reason for him to do this.

[Adam496]

I was on my way home from snowboarding today about 8pm. I stopped at D+D to let my friend get something and I was planning on stopping at a pizza place to get a slice or two a little down the road after.
Well on my way out of D+D I take a left, leaving plenty of space for the up and coming car (cop car). He immediately he speeds up and is up my rear of I was thinking he was reading my plates or I was going to get cherries. So I continue on my way, he is still there. So pull into the pizza place and go in. While I am getting my food I am watching him circle the parking lot.
My story may seem a little vague but I know for a fact I did nothing wrong. Do you think he was seriously trying to watch me for a mistake or just messing with me?