OK, so he fails to signal, they pull him over, and he opens fire. If this was a trap for the police, it seems like he would use something better than failing to signal as bait. Maybe he just snapped.
Sort of a b.s. reason to pull him over.... just like the typical “left lane for passing only” west Texas I-10/20 often used pretext. It would be interesting to search through the forfeiture records to see how much is stolen from the highway users.
*This in no way even remotely is an excuse for what the murderer did.
They were looking for him for some reason.
Something in the truck? Something he was trying to hide?