Zero Fail: The Rise and Fall of the Secret Service by Carol Leonnig:
Routine as it was, Secret Service agent Bill Green had nevertheless spent five days mapping out a detailed security plan prior to the outing. Green, the advance agent for the visit, had made sure protective research agents ran background checks on everyone who would meet the president or come close to him. Green’s team had inspected every part of the hotel, from the garbage bay to the basement, for hidden threats. They had mapped out every step Reagan would take: from the VIP entrance to the elevator to the holding room to the stage and back.
This “routine” visit would require the teamwork of sixty-seven agents. Together they would create rings of human, metal, and technological barriers to shield “the Man.” More than two dozen more would stake out positions in the ballroom, rooftop, hallways, entrance, and perimeter. Many more would help search for explosives with bomb-sniffing dogs, run background checks on guests and hotel workers, monitor crowds outside, and help clear streets for the motorcade. Green had visited the site during all five days of planning and done a walk-through the morning of the visit.
The White House advance man, Rick Ahearn, hoped to have the traveling press at the front of the ballroom, but the union complained that the cameras would block their own members’ view and asked to have them pushed back. Some enterprising cameramen from the three big local television stations, however, ended up finding a much closer spot to get a good close-up of the new president. They staged themselves outside the Hilton, just fifteen feet from the back of Reagan’s limousine, in a viewing area the public could reach without being screened by agents.