[99] He was sworn in by U.S. District Judge Sarah T. Hughes, a family friend.[100] In the rush, Johnson took the oath of office using a Roman Catholic missal from President Kennedy's desk,[101] despite not being Catholic,[102] due to the missal being mistaken for a Bible.[102] Cecil Stoughton's iconic photograph of Johnson taking the presidential oath of office as Mrs. Kennedy looks on is the most famous photo ever taken aboard a presidential aircraft.[102][103]
Johnson was convinced of the need to make an impression of an immediate transition of power after the assassination to provide stability to a grieving nation in shock.[104] He and the Secret Service were concerned that he could also be a target of a conspiracy,[105] and felt compelled to rapidly remove the new president from Dallas and return him to Washington.[105] This was greeted by some with assertions that Johnson was in too much haste to assume power.