I will need to review the episode later tonight. My memory of the shooting is that the gun was fired from the passenger side. I, also, remember that Holmes identified the gun as an AP-15. This is a carbine rifle. In this video, the shooter is using both hands to use the rifle.
Maybe I am not able to conceptualize this, but I can't see how a person can simultaneous fire a rifle and drive a car perfectly straight in a lane.
And, I love how Detective Bell's car manage to find the one construction zone with a ramp so that the car could execute a perfect stuntcar crash.