Clint Eastwood is to direct a true-life tale of tourists who thwarted a terrorist attack.

The 'American Sniper' filmmaker will helm an upcoming movie based on Anthony Sadler, Alek Skarlatos, Spencer Stone and Jeffrey E. Stern's book 'The 15:17 To Paris: The True Story Of A Terrorist, A Train, And Three American Heroes'.

The book chronicles the events of 2015, when Anthony, Oregon National Guard member Alek and Spencer - a US Air Force airman who was trained in martial arts - were travelling by train from Brussels to Paris when an ISIS terrorist, armed with a loaded gun and ammo, boarded the vehicle with the intention of killing as many people as possible. The three Americans charged at the man and were able to overpower him as he prepared to launch his attack.

Dorothy Blyskal has adapted the script from the book, and Clint is planning to begin casting now and wants to start filming the Warner Bros. picture later this year.

Whoever gets cast in the film will be expecting to work hard, as Tom Hanks - who had the lead role in 'Sully: Miracle on the Hudson' - recently admitted the 86-year-old filmmaker treats his actors ''like horses''.

He said of working with the actor-turned-director: ''You certainly don't want one of those Eastwood looks.

''He treats his actors like horses because when he did the 60s series 'Rawhide', the director would shout 'Action!' and all the horses bolted. So when he's in charge, he says in a really quiet soft voice, 'All right, go ahead,' and instead of shouting 'Cut!' he says 'That's enough of that.' It's intimidating as hell!''