Got pulled over!

I was driving with a friend of mine on the highway to pickup some other people to go chill.
The very far left lane on the highway (4-5 lanes) was free. I was doing ~140-150 km/h just cruising there. Then goto the second right lane because I had to go off the last exit or else it went to another highway. So I'm following a van doing 110km/h. All of a sudden I see a cop behind me tailgating me for about 20-30 seconds. Then his sirens go on and he gives me the highbeams!
He asked me where I was going, told me I was going pretty fast, got my license and registration and asked if I got a ticket before (well I didn't so I said no). He went to his car, went to check some stuff out, then said that I should slow down, that's the speedlimit is 100 and I should do 100, it's not worht the ticket!
I said thank you and left. PHEW, thank *** he didn't radar me down...What I don't get is, did he see me doing 140-150 and zoom by him because I saw no cops, and the highway wasn't that full for them to hide. He came behind me out of nowhere. and 110 isn't fast at all. that's what EVERYONE drives at here. hardly ever met anyone who DID speedlimit on the highway! damn that was scary...