I think it was more personal than that:
According to witnesses a car crashed into the ministers car from behind. Then the assassin got out of the car, walked over to the ministers car, and fired from close range.
---According to witnesses a car crashed into the ministers car from behind. Then the assassin got out of the car, walked over to the ministers car, and fired from close range.---
Road rage.
But that doesn't square with the shots to the driver or the other groups in the door or window. Wouldn't do that from point blank range. Perhaps there were two shooters? (Grassy knoll theory) One stops the vehicle by taking out the driver. Shooter #2 following offers the Coup'de grace by walking up and finishing the job. DOA.