Sgt. Davis, of the Dallas Police Department, believed he had prepared stringent security precautions, in an attempt to prevent demonstrations like those marking the Adlai Stevenson visit from happening again. About the book: https://www.amazon.com/gp/product/1439192995/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=1439192995&linkCode=as2&tag=tra0c7-20&linkId=f1ac6621f719706f064aa9749a863b28
The previous month, Stevenson, the United States Ambassador to the United Nations, was assaulted by an anti-UN demonstrator. But Winston Lawson of the Secret Service, who was in charge of the planning, told the Dallas Police not to assign its usual squad of experienced homicide detectives to follow immediately behind the President's car. This police protection was routine for both visiting presidents and for motorcades of other visiting dignitaries. Police Chief Jesse Curry later testified that had his men been in place, they might have been able to stop the assassin before he fired a second shot, because they carried submachine guns and rifles.
An investigation by the House Select Committee on Assassinations (HSCA) in 1979 concluded that "the Secret Service was deficient in the performance of its duties." The HSCA stated:
That President Kennedy had not received adequate protection in Dallas.
That the Secret Service possessed information that was not properly analyzed, investigated, or used by the Secret Service in connection with the President's trip to Dallas.
That the Secret Service agents in the motorcade were inadequately prepared to protect the President from a sniper.
The HSCA specifically noted:
No actions were taken by the agent in the right front seat of the Presidential limousine [ Roy Kellerman ] to cover the President with his body, although it would have been consistent with Secret Service procedure for him to have done so. The primary function of the agent was to remain at all times in close proximity to the President in the event of such emergencies.
Clinton J. Hill (born 1932) is a former United States Secret Service agent who was in the presidential motorcade during the assassination of John F. Kennedy on November 22, 1963, in Dallas, Texas. After Kennedy was fatally shot, Hill ran from the car immediately behind the presidential limousine and leapt onto the back of it, holding on while the car raced to Parkland Memorial Hospital. This action was documented in the famous Zapruder film. Hill is the last surviving passenger of the presidential limousine which arrived at Parkland Hospital.
Hill was born and raised in North Dakota. His birth parents homesteaded near Roseglen and he was born in Larimore, North Dakota, then placed in an orphanage in Fargo where he was adopted by Chris and Jennie Hill at three months of age. Hill's new family took him to Washburn where he eventually graduated from Washburn High School. He also attended Concordia College in Moorhead, Minnesota, where he played football, studied history, and was a 1954 graduate. After college, Hill was assigned to the Denver office of Secret Service in 1958 and served on the detail for President Dwight D. Eisenhower. After John F. Kennedy was elected President of the United States, Hill was assigned to protect the First Lady, Jacqueline Kennedy.
President Kennedy was assassinated on November 22, 1963, in Dallas, Texas, during a motorcade through the city, en route to a luncheon at the Dallas Trade Mart. The President and Mrs. Kennedy were riding in an open limousine containing three rows of seats. The Kennedys were in the rear seat of the car, and the Governor of Texas, John Connally, and his wife, Nellie Connally, were in the middle row. Secret Service agent William Greer was driving and the president's bodyguard. Roy Kellerman, was also in the front seat.
Hill was riding in the car immediately behind the presidential limousine. As soon as the shooting began, Hill jumped out and began running to overtake the moving car in front of him. He climbed from the rear bumper, crawling over the trunk to the back seat where the President and First Lady were located.
Hill grabbed a small handrail on the left rear of the trunk, normally used by bodyguards to stabilize themselves while standing on small platforms on the rear bumper. According to the Warren Commission's findings, there were no bodyguards stationed on the bumper that day because
...the President had frequently stated that he did not want agents to ride on these steps during a motorcade except when necessary. He had repeated this wish only a few days before, during his visit to Tampa, Florida.
The notion that the President's instructions in Tampa jeopardized his security in Dallas has since been denied by Hill and other agents.