Here is a google street view of Hoffman's view of the triple underpass from the center lane of Stemmons.
The google camera here is say 7 ft above the tarmac, whereas Hoffman's eye (when he was driving his Falcon) would have been only say 3 ft 10 inches above the tarmac.
On the other hand, the Falcon might have been in the right-hand lane (ie next to the right-hand breakdown lane),
which would have enjoyed a better view than the view from the center lane.
And in Bell's footage we can see a car passing the Falcon, & that car is on the other side of the Falcon, ie it is in the left-hand lane or it is in the middle lane.
Hence the Falcon is in the center lane or in the right-hand lane. I think the right-hand lane.
I had to use the google view from a long way south of where i wanted. I wanted the view from where Hoffman was when the JFK limo first exited the underpass.
This would have been when Hoffman's Falcon was directly over Main St. But the new on-ramp blocks that view.
When JFK first exited the darkness of the underpass, ie into the sunshine, Hoffman would i reckon have been able to see the limo, at least until the limo quickly disappeared below the eastern concrete barrier of Stemmons.
Hoffman's passenger would have had a better view than Hoffman.
In Bell's footage we see that the passenger has sprung out before the Falcon has come to a complete stop.
Hence we can safely say that the passenger saw the limo, & the flashing lights, & heard the sirens.So, the passenger won't have known about the shots, but he could see that something was cooking.