Destroying the limo and windshield asap seems to be a poor choice by the FBI if they were following the Hoover directive that the public must be convinced there was no conspiracy.
Unless …there was something particular about the damage to the rearview mirror frame and windshield crack which they feared could be analyzed with some method to show micro traces of metallic fragments that differed from what would be left by MC bullet fragments.
Or an analysis that could determine with certainty that the crack in the windshield could only be caused from a projectile hitting the front of the windshield. ( or that it was a hole)
If there was a shot from the front of the limo, was Greer the target?
Killing the driver of the limo would probably bring the limo to a stop or slow down , thus affording an easier kill shot aimed at JFK by a sniper from behind the limo.
Why did not a rear shooter take the shot at Greer? Perhaps because Mrs C and Jackie were obstacles and or the shooters did not wish to harm the popular Jackie or the wife of the neocon pro MIC governor. The only target was the “traitorous communist sympathizer” JFK.
Shooting from the east side of the Triple U bridge (with a suppressed rifle), that snipers LOS angle to Greer was a fairly safe shot that could avoid hitting Mrs C, Governor C , or Jackie( presuming the shooter was relatively skilled at shooting laterally moving targets)
If there was a front shooter located at the east side of the Triple overpass , his shot aimed at Greer , would be a target moving laterally at 20mph. So the shooters lead adjustment might have been too much and the bullet struck the windshield instead of Greer.
Ironically, the resultant effect was the same, as Greer reacted by taking his foot off the accelerator and the limo slowed down to 8mph (or almost to a stop by some witness accounts)
Imo, Greer was NOT a conspirator , but was reacting in confusion as to where the shots were coming from. Therefore, if there was a shot aimed at him, it was for purpose of stopping the limo or at least to slow it down, affording the a sniper from behind the limo an easier kill shot at JFK.