I have read it and do not buy it. That picture is fond in the 6th Floor Museum and was taken at about 150 yards past the triple overpass nand not in Dealey Plaza.
No problem, you’ve read the Menninger book, and formed your opinion. I respect our differences of opinion here.
As far as your additional description of the picture ... does not disprove Donahue’s analysis even if it was taken where and when you described it as being taken. - SS agent, armed, in SS detail car that was directly behind the JFK limo when it was in Dealey Plaza. Agent able to stand in car.