> note the absence of road flares, safety signs, warning cones or any other device warning motorists to slow down.
At time index 25:55 in the FBI video you can see a police vehicle in the southbound lane north of the roadblock. There are also police vehicles south of the roadblock. The AO was clear.
(reference: https://www.youtube.com/watch?v=aAGxDWKrjPQ )
To me that bad things start happening when he decides to go off the side of the road. It is interpreted by the LEOs as hostile, and sets up the deadly shooting that follows.
Had he had ample visibility to the roadblock and slowed down, then stopped in the road, I think this might (maybe, I wish) been avoided.