[Fiji Hill]

Call me crazy, but I still believe it was a SS agent who ACCIDENTALLY fired that explosive head shot with his AR-15 from the chase car.

Was the Secret Service using AR-15's at the time?

[Obama_Is_Sabotaging_America]

I don't know the details, but I DO know there was a least one agent with an AR-15. Here he is:

I do believe that when the chase cars began to speed up after Oswald's neck/shoulder shot on Kennedy, the car lurched causing the agent to inadvertently pull his trigger.