He was tailgating me and SAW me do something illegal so why didn't I get pulled over by the state-police?

Today I was driving back from somewhere on a highway. It's a 2 lane highway and the speed limit is 50. I was in the left lane going exactly 50 because I noticed the state police. I kept looking in my rear-view mirror and then he was right behind my @ss! I mean literally! If I slowed down even a little, I know for a fact he would've hit me. So, I was trying to be a good sumaritan and I started to speed up and I went up to 60 and he was still right behind me. bumper to bumper! So I decided to signal and switch over to the right lane because he wouldn't move to the right lane and go around me. and as i did that, i didn't even look and I almost got hit by a car in the right lane. and that car started to honk and i was shaking like crazy because i didn't see her. So now I'm on the right lane and I look over to my left and he is mouthing me and I think he said "What the hell are you doing?!" And I thought omg I'm screwed, he is going to pull me over. But after he "mouth" those words (or whatever he said) he sped off! I felt so relieved but why didn't he stop me? I'm sure the the car behind me thought the cop was going to stop me too! I'm glad he didn't but I want to know why? was it because he felt guilty for tail-gating me?