Tom Hanks is opening up about a terrifying experience from his storied acting career.

While shooting the 2013 biographical drama Captain Phillips, which tells the story of the 2009 siege of the Danish–U.S. cargo ship Maersk Alabama by four Somali pirates, Hanks had to shoot what he now calls “the most truly scary, intense, real-life scene” of his career, he recounted on the Conan O’Brien Needs A Friend podcast.

“Four of the scariest human beings I have ever met come in, and they are screaming at us,” Hanks told host Conan O’Brien. “They are slapping us. They are hitting us. They are pushing us down, and they’re holding real guns in our faces, screaming at us. It was honestly — we are all bug-eyed with some form of terror. Even though we know it’s a movie, that is removed because — guess what? — we all went there.”

To make matters worse? Hanks and his costars hadn’t even met the actors hired to play the pirates before filming the violent takeover.

“We’re overweight, old, middle-aged guys who are gonna be taken over by these pirates,” Hanks explained, “and we have never met the guys who play the pirates. We don’t know who they are. All we know is that they are coming, because the way [director] Paul Greengrass shot that, he had cameras on us and cameras on the four guys, [Barkhad Abdi, Mahat M. Ali, Barkhad Abdirahman, and Faysal Ahmed] — all the guys. We have never met them, and they are firing automatic blanks, you know, machine guns. We hear all this stuff that’s going on. We don’t see anything until the camera outside the bridge of the Maersk Alabama.”

Captain Phillips plays out like an anatomy of the real-life siege, and it is indeed harrowing. Hanks and costars Michael Chernus, David Warshofsky, and Corey Johnson are shot at, chased, bludgeoned, and manhandled. In real life, as in the film, all the hostages were rescued, with the only three casualties being the pirates. But even recreating the events has had a lasting effect on Hanks.

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“This initial scene went on for about 20 minutes, because Paul does this thing where he has secondary and third cameras that don’t start shooting until later on,” he explained. “So film is always rolling, and then one camera will go quickly reload and then join back in the scene. And we are right there because the camera’s on us, and it’s working us. So four of the skinniest, scariest-looking guys — their eyes were all bloodshot, they all had these teeth, they were all built like wires, they had muscles like rope, they’re dressed in rags, and they’re holding AK 47s on us, and they’re screaming at us.”

The assault “went on and on and on, relatively unrehearsed” until finally, Hanks said, “Paul says, ‘All right. All right. That went well. What I’d like to do is just take it back and come back in.’” Hanks relayed that he and his costars were still genuinely shocked by what had just happened, but one of the actors playing a pirate managed to break the tension. “Mahat says, ‘I can’t believe I’m working with Forrest Gump,’” Hanks recalled.

“He just tried to kill you!” O’Brien shouted in disbelief.

“Once we got that done, we were just guys making a movie,” Hanks explained. “It was fantastic. But that’s an example of, there was a moment where you have to do all this suspension of the reality of what it is, and all you can do is go there.”

Captain Phillips was a huge box office success when it was released in 2013, and it picked up six Academy Award nominations, including Best Motion Picture of the Year and Best Performance by an Actor in a Supporting Role for Abdi.

Barkhad AbdiMany who were present on the Maersk Alabama for the real-life hijacking attempt disputed the film’s portrayal of events. A group of 11 shipmates even sued the owners of the vessel, claiming Captain Richard Phillips directly put their lives at risk.

“Phillips and Maersk put the men in harm’s way, in spite of warnings to keep them out of the pirate-infested waters. They did so for financial gain,” an attorney for the litigants said at the time. The suit was eventually settled in 2017.