Fifty years after John F. Kennedy's assassination, director Peter Landesman transports the viewer behind the scenes to witness the chaos, panic and grief of the infamous event in his new movie "Parkland," which premiered in Venice Sunday.

"The film is not about conspiracies. We chose to tell a truthful story, one we know happened to those particular characters, the ordinary people caught up in the wake of this historical event," first-time director Landesman said.

"Parkland" opens with the famous home movie footage inadvertently captured by Abraham Zapruder showing Kennedy being shot as his motorcade passes through Dealey Plaza, Dallas, on November 22, 1963.

It then follows the secret service agents on the mad rush to the Parkland hospital and the medics who battle to save the US president, before shifting the focus to the hunt for suspect Lee Harvey Oswald and his murder.

Kennedy and Oswald become secondary characters in a tale which focuses on "ordinary bystanders," in particular Oswald's brother Robert, played compellingly by James Badge Dale, who is left to grapple with what happened.

"Robert's character for me is the most powerful, he sums up the whole," Landesman said.

"Out of the blue this thing hit him. He wakes up one day and discovers his brother is the devil. James's performance for me was otherworldly," he said.

"Parkland" walks a fine line between documentary and fiction.

The result is some engaging scenes -- like the one in which the agents are forced to rip seats out of the Air Force One plane to get Kennedy's coffin on board.

But the plot at time is dragged down by some rather banal dialogue and over dramatic music.

Jacki Weaver, who plays the Oswalds' mother, brings relief with her venomous, batty performance as Harvey Lee's defender, as she insists time and again he is a secret service agent who has been stitched up for the murder.

"There are certain events in American history, from Pearl Harbour to 9/11, which fascinate because of the reaction not of the iconic people but the bravery of the average ones, those in the shadows," producer Matt Jackson said.

Landesman said he gained access to police transcripts and police recordings of the conversation between the Oswald brothers, and travelled to meet with surviving secret service agents to make his screenplay as accurate as possible.

The team got permission to use the original Zapruder footage of the murder.

"The Zapruder family have been very secretive in the past, but opened up to us and even came on set, bringing a spirituality to the story," he said.

Landesman brushed off accusations of an almost gratuitous use of blood in the emergency room scene, describing the film as "very powerful, Shakespearean."

"There became a moment when Parkland became a state of mind for us. It became a place where hope and dreams go to die," he said.

"For 50 years we have been caught up in suppositions and the myths surrounding what happened that day will never end -- they'll probably grow.

"But in this film we wanted to focus on the raw truth of survival," he said.