History-Changing FBI Whistleblowers Reveal Themselves in '1971'

On March 8, 1971, a group of anti-war activists broke into an FBI office in Media, Pennsylvania, and changed the course of history.

The burglars wound up blowing the whistle on illegal surveillance and bullying tactics employed by J. Edgar Hoover and his government agency — and despite one of the biggest FBI dragnets ever, the perpetrators were never caught and their identities remained secret… until now.

The new documentary "1971" reveals these former political radicals as they tell their story on film for the first time. At the time of the break-in, anti-war activists believed they were being watched by the FBI. Bonnie and John Raines, a married couple with three children, had participated in rallies and were photographed by suspected govenment agents. That prompted them to join the group, which eventually swiped more than 1,000 documents.

[Related: 'Jodorowsky's Dune' Trailer Uncovers the Wildest Sci-Fi Movie Never Filmed]

"If the FBI was suppressing dissent, it was as important to expose that as it was to end the war," says journalist Betty Medsger, who is responsible for exposing the burglars's identities. She wrote the new book "The Burglary" and worked closely with "1971" filmmakers.

Billing themselves as 'The Citizens Commission to Investigate the FBI,' the members took serious risks to deliver the stolen FBI documents to the press. "We knew that if we got caught, we were going to face very serious prison time," says John Raines in the film (as seen in the trailer).

"Break into an FBI office, remove files, and mail them to newspapers," says Bonnie Raines of the plan. It was not haphazard. They cased the FBI building in Media for weeks, tracking comings and goings and drawing up detailed maps and a plan.

Multiple setbacks nearly halted the operation. "A couple of weeks before the break-in date, one person in the group dropped out — simply walked away. This person knew every detail of their plans. The risk that he would expose them was huge. They went ahead anyway," says "1971" director and producer Johanna Hamilton. "The break-in itself almost didn't happen. When the chief lock-picker arrived, he found the lock on the FBI's door was different than the one he had been practicing for. So the whole process was much more complicated and tenuous than they originally thought," she tells Yahoo Movies.

[Related: 'Big Men' Trailer Drills Into Big Oil, Big Money, and Big Danger]

Once the documents were taken, the group spent days scanning them to find evidence of FBI wrongdoing, according to a recent New York Times report. They sent copies of the most revealing documents to journalists, one of whom was Medsger of the Washington Post. She was one of few journalists who acted on the information.

The biggest discovery was finding that Hoover ran a covert operation with the code name COINTELPRO, under which the FBI would survey, infiltrate, discredit, and disrupt political groups and U.S. citizens deemed "subversive." Much of the activity was illegal.

[Related: Sibling Rivalry Meets Rock Stardom in 'Mistaken for Strangers' Trailer Premiere]

The documents revealed that a wide array of postal workers, police, and even switchboard operators were used as FBI informants. Martin Luther King Jr. was a major target of COINTELPRO, with agents having him under surveillance and repeatedly bugging his home and hotel rooms.

The burglary which exposed COINTELPRO led to the first-ever congressional investigation of U.S. intelligence agencies, and as a result the operation was terminated.

"What is consistently amazing to me is the fact that only one of the documents they stole contained the caption COINTELPRO. It was that one document that would lead to the full revelation of FBI dirty tricks," says Hamilton.

Another stunning revelation: Hoover's program had been running since 1956. "By 1971 so many people and groups had been put under surveillance," says Hamilton. "Basically there was blanket surveillance of African Americans — both well known, like the Black Panthers, and less known, everyday people, students, people who were active in communal African-American life."

"1971" debuts at the Tribeca Film Festival in New York on April 18.

Follow me on Twitter (@meriahonfiah)