I was commuting to work this morning, on a 4 lane hwy (2 each direction) and speed limit was 65. It was moderate rush hour traffic and I was in the fast lane going 71 and passing the slower lane that was mostly going about 65-66. Like I said it was moderate traffic, so no real opportunity to speed or anything, just going with the flow and the fast lane was going a little faster. I start approaching an over pass and the Ka starts going off, faint at first and building quickly. I suspect a LEO on the overpass or on the on/off ramps but don't see any. I check rear view mirror and I see a grey Ford explorer 1/8 mile behind me but coming up on me. As I get to the over pass it has built to full bars on Ka and then it pretty much abruptly stops as I go under it. By this time I had taken my foot off the gas and was just coasting down to posted speed limit. The cars in the slow lane start pulling ahead of me, so I ease it back up to about 70, and by this time the explorer is on my tail. Then Bam, full bars, IO. I take foot off gas and coast down to posted and pull into slow lane. The explorer pulls by me and I look at the vehicle closely. Absolutely no markings of a LEO, but I can see a mounted laptop open in the passenger seat. Driver is not in any uniform and I don't see any hidden emergency lights or back seat bars etc. The explorer driver doesn't look at me and pulls by and keeps going. So what happened? I think the explorer was the LEO (because of the open mounted computer on the passenger seat), and he may have seen my window mount RD and hit me with instant on so I would slow down and pull over so he could keep speeding??? Because why would he use instant on when he was on my tail and going my speed. Any other thoughts? it was weird.