Four days after he had approached Kennedy in the church, Pavlick, 73 at the time, was stopped by Palm Beach officer Lester Free for a marked lanes violation, said Rust.
"If he hadn't stopped him for crossing a white line, history might be very different," he said.
Rust found out that Pavlick purchased explosive materials in New Hampshire. He told special agent John Marshall, "We've got a live one."
They visited Pavlick in jail and he gave them permission to search his Buick where he had 10 sticks of dynamite rigged with a switch to set it off, according to CapeCodOnline.com.
"We made him a federal prisoner and drove to his motel room," Rust said.
In the room, Rust found binoculars that were used to watch the movement of Secret Service agents in a nearby motel and a letter written by Pavlick that he calls the man's last will and testament.
"That's where he explains why he had to kill the president," Rust said.
In the letter, Pavlick accuses the Kennedy family of buying the presidency and Catholics of failing to obey the same laws as all Americans.
"Now that the presidency has been sold to the Kennedys, they must be stopped by any and all means possible," the letter states.
"My country's best interests are, to me, greater than my own life," Pavlick wrote.
"You can see this guy was vicious, intelligent and crazy," said Rust.
In court, Pavlick was ordered to undergo psychiatric evaluation.
"(The doctor) testified that Pavlick was not mentally competent to stand trial," Rust said. "He was a functioning nut in my estimation."
Rust says Pavlick insisted he was sane, so the judge allowed the defense to hire its own psychiatrist.
After 5 to 10 visits with Pavlick in jail, that doctor was summonsed to court, but refused to give his name or testimony until Pavlick was removed from the courtroom because he was afraid of him.
"When he was out of the courtroom, (the doctor) gave his opinion that Pavlick was mentally incompetent and a homicidal maniac," Rust said.
For several years, Pavlick was moved from federal hospital to federal hospital and at one point was sent back to New Hampshire to a state facility, Rust and Sweeney said.
In 1966, three years after Kennedy was killed in Dallas, the Manchester Union Leader in New Hampshire, led by right-leaning publisher William Loeb, wrote a series of editorials pushing for Pavlick to be released, Sweeney said.
Pavlick was released and started stalking Murphy and his family.
"He would come up periodically and park by Murphy's house," Sweeney said. "He would sit and stare at the house. I would come up and check him out and stare back at him. We had no stalking law. He wasn't disturbing the peace. He wasn't really doing anything. Murphy felt he had no protection."
Royle said there were others who didn't agree with what Kennedy stood for and who were in Dallas that day handing out leaflets that said, "Wanted for treason," and advertisements appeared in newspapers calling him soft on communism.
"You realize watching that and watching all the contemporary footage, just how much of a polarizing figure (JFK) was," Royle said. "We tend to think of the Kennedys with this Camelot glow around them. They were incredibly glamorous people, extremely intelligent and articulate, but they polarized the country. There were people who loved them and people who hated them."