As Zac Efron's character pumps frantically on a dying JFK's chest, gets elbows deep in blood and barks out medical terms in the upcoming film Parkland, the young actor says he never really knew when the camera was on him.
The style in which director Peter Landesman chose to shoot much of the movie – which focuses on the minor characters around President John F. Kennedy moments after he was assassinated – was one which Efron hadn't encountered before.
"We kind of recreated the moment as honestly as possible, in its entirety and kind of went through it the way it would have happened," he said while promoting the film at the Toronto International Film Festival.
"We weren't particularly aware of where the camera was or what was being filmed, so the only option was to just kind of do it … and stay in it and focus. It was really fascinating. There were moments when for all intents and purposes I thought I was there."
Efron plays Dr. Charles (Jim) Carrico, the young resident on duty when a wounded JFK arrives at the Dallas hospital which gives the movie its name.
Landesman, a former investigative journalist, was largely a "fly on the wall" for the hospital scenes, letting the cast really dig into the characters they were playing without much interruption, said Efron.
"I was operating on this guy, it felt like it there was a real guy there," he said. "It was intense. After every take I was shaking uncontrollably … the effect of this film lasted for several days."
Efron's character is later joined in the operating room by veteran Dr. Malcom Perry, played by Colin Hanks. In an ironic twist of fate, both doctors tried to save first the president and later his assassin, Lee Harvey Oswald, played by Jeremy Strong.
Hanks said the entire process in which Parkland was filmed was different, allowing the movie to provide a fresh take on a much-examined story.
"It was really all about us doing whatever the scene required for however long it needed to go," he said. "There was not this concern about 'Oh I better be good because it's my shot,' you just never knew."
"It helped us in that we were acting without acting. It was really just trying to be as much in the moment as possible."
Creating the feeling of real-time urgency around a historical event which took place 50 years ago was precisely what Landesman was aiming for while making the film.
"There was nothing performative, and there was nothing anticipated, there was nothing planned," he said of the event, which stunned the world, and its aftermath.
"It was very important for everybody … to create a sense of rawness. Almost as if it was happening now, that was the idea."
Parkland also features Paul Giamatti as the bystander who famously filmed the president's shooting, Billy Bob Thornton as a surly Secret Service agent, James Badge Dale as the brother of JFK's assassin and Jacki Weaver as the shooter's mother.
It opens in theatres Oct. 4.