I think just you also need to be careful of the word following.
If a car is driving down the road and there is a car in front, is it following it? The pedants on here will say that is the correct use of the English language. Sensible people would say it is simply driving down the road. The crash scene is over half a mile away. If the bike turns one way the cop van another, this footage means nothing.
I've seen the footage. The bike zooms past at what looks like a high speed. A few seconds later a police van appears going in the same direction but it doesn't appear to be going as fast or have flashing blue lights. Half a mile isn't a great distance particularly in a vehicle. Coincidence both vehicles going in the same direction, one a police vehicle? Possibly.