DALLAS Dr. Kenneth Salyer was a 27-year-old resident at Parkland Hospital on call for head injuries when he got word a new patient was being rushed to the ER. "A nurse ran into the room and said, 'The president's been shot,'" Salyer says. But nothing prepared him for what he saw. "He was still breathing," he says. "It's sort of agonal, labored, close-to-your-last sort of breaths. But he still was breathing." When the president's clothes were removed, Salyer was surprised by what he found. Kennedy, who suffered from chronic back pain, was wearing a heavy, corset-like brace that went from...