[Jackson57]

JFK was already dead at that point, so little need for Secret Service protection, plus that is a military hearse, so the body is being moved on a military base.

[Lonesome in Massachussets]

Jackie and RFK were in the hearse, according to the lede and the ambulance was traveling from Dulles to Bethesda, so it would be traveling on public highways.

[Responsibility2nd]

Jackie was in that ambulance with her husband. So were the Secret Service agents

Last month - on the History Channel - there was a rather interesting show about Secret Service agents who were working night and day with the first family before, during and after the assassination.

They - to this day - still teared up as they personally related the events as they happened.

I got a lump in my throat just watching them tell their stories.

[Venturer]

Bet me: They had Secret Service with that body every minute.