You were driving around by yourself in the middle of a civil war. Could not possibly fathom why. Saito was hiding while his men were coming to retrieve him to take him back to the MoI. Also very curious how you drove up to him and jumped out of your car at the verrrrrrry corner of the map. He was the only person back there and you just happen to come upon him...odd.
Saito being shot has zero to do with you, however, I will explain since you seem to think there was some slight against you. Saito was shot from across the map by a random NCO, we do not allow for JFK pk's unless otherwise approved. Realistically, Saito could have gotten away with no punishment, whether temp or permanent, and been totally within our precedence and our guidelines. I, however, believed he should have something happen to him. So a temporary PK was issued to demonstrate him being JFK'd in the street during a civil war. These are done on a case by case basis.
TLDR; You were driving around by yourself as the VP like a goober and got gunned down when you happend upon Saito in the corner of the map where he was by himself hiding. You were gunned down as you were in a military uniform the military and MoI were in both in total KOS mode. Saito was JFK'd by a non-involved party and JFK's are not permitted unless otherwise approved. The end.
Please let me know if you have any questions.