hardtop carrying warrant officer Ira Gearhart, who carried the Presidential Emergency Satchel, also known as the "nuclear football"), the official party bus (Continental Trailways bus) carrying Evelyn Lincoln, the president's personal secretary and rear admiral George G. Burkley, the president's physician), several extra cars and police escorts. Abbreviations used above include: SA: Secret Service Special Agent SAIC: Special Agent in Charge ASAIC: Assistant Special Agent in Charge ATSAIC: Assistant to the Special Agent in Charge Secret Service driver agents operated through their own command chain. Driver agents were typically recruited from the uniformed White House Police Force. Presidential motorcade route The motorcade route took a left turn from the south end of Love Field to West Mockingbird Lane and continued through to central Dallas. It progressed down Main Street, then at 12:29 p.m. CST turned right (westbound) into Houston Street, fatefully entering Dealey Plaza. The presidential motorcade began its route without incident, stopping twice so that President Kennedy could shake hands with Catholic nuns and schoolchildren. This exact route cannot be driven today as several of the roads have changed. The motorcade approached the Texas School Book Depository, and then made a sharp 135 degree left turn onto Elm Street, a downward-sloping road that extends through the plaza and under a railroad bridge at a location known as the "triple underpass." The giant Hertz Rent-a-Car clock on top of the Schoolbook Depository building was seen to change from 12:29 to 12:30 as the limousine turned into Elm Street. Most of the witnesses recalled that the first shot was fired after the president had started waving with his right hand. Several onlookers recalled hearing three shots, with the second and third shots bunched distinctly much closer together than were the first and second shots. Witness testimony varies; some heard only two shots but others claimed to have heard as many as eight. The Zapruder film shows the president reemerging after being temporarily hidden from view by the Stemmons Freeway sign at Zapruder film frames 215 to 223, and his mouth has already opened wide in an anguished expression by frame 225. He has already been impacted by a bullet that struck him in the upper back and exited his throat, and his hands clench into fists. He then quickly raises his fists dramatically in front of his face and throat as he turns to the left toward his wife. Secret Service