Before we move forward, we're obligated to tell you that there are Once Upon a Time in Hollywood spoilers ahead. Since you already know from the trailer that Leonardo DiCaprio handles a flamethrower, we've added a clip below featuring that scene, to distract you from accidentally reading other plot details involving a flamethrower—okay, we've said too much!
In an interview with HuffPo, Once Upon a Time in Hollywood stunt coordinator, Robert Alonzo, revealed that DiCaprio was apprehensive about shooting the scene from his character Rick Dalton's World War II film The 14 Fists of McCluskey, in which he uses a flamethrower to set a group of Nazis ablaze.
"Leo was not very gung-ho with all the flamethrower stuff," Alonzo said. "Literally, he doesn’t want to hurt anyone. And I completely understood it. Normally you use a stunt person in that spot to be able to manage firing a flamethrower at somebody."
Alonzo understood the psychological toll it took on Leo to torch the stunt team for a sustained period of time, even if they were covered in flame-retardant gear. "When I did Tropic Thunder, Nick Nolte [accidentally] fired a flamethrower at me…This time, [Leo] is actually lighting them up and holding a flame to them for about seven to eight seconds as the flamethrower is traversing back and forth around eight guys that he’s never met. That is psychologically difficult to do, so kudos to him on being able to stay in character and do that scene."
To get DiCaprio comfortable with executing the stunt, Alonzo says he held a demonstration where he set himself on fire. After seeing that his stunt coordinator was fine, Leo had everyone give him a round of applause, and that was enough to get the 44-year-old actor in the right frame of mind to film the scene.