On August 21, 2015, childhood friends Anthony Sadler, Alek Skarlatos and Spencer Stone were just three Americans enjoying a European adventure.

They had planned to stay in Amsterdam an extra day, but changed their minds last minute and boarded the express train to Paris. They didn't expect to come face-to-face with an armed man who would open-fire in their cabin, which was carrying 554 passengers. But they did.

They didn't have much time. Stone tackled the gunman first, and worked together with Sadler and Skarlatos to overpower the man and effectively thwart the attack.

The gunman, who was identified as Ayoub El-Khazzani, was a Moroccan national who had been on the radar of several European counterterrorism agencies. He was carrying several weapons, including a Kalashnikov, automatic pistol and razor blades.

However, the three American men - plus one British man named Chris Norman - were able to successfully stop El-Khazzani before the attack turned fatal. Stone sustained serious injuries which required surgery. But they prevented something far worse.

At the time, Sadler was just a senior in college at Sacramento State University, while Skarlatos and Stone were in the military. The three had been friends since middle-school.

Now, the heroic trio are starring in the latest Clint Eastwood film, "15:17 to Paris." They play themselves and recount the entire event on the big screen.

The film will be released in theaters nationwide on Feb. 9.

CNA recently interviewed Sadler, Skarlatos and Stone. Below is the full interview, edited for clarity.

Can you share a little about your faith and the impact it has had on your lives?

STONE:    I was raised in a Christian home, my entire life. Went to church every Sunday with my mom and brother and sister and Wednesday night church, too. I believed [in God] my entire life. God for me is someone that is always there and always will have my back, whether it's a good or bad situation. And it's in the Bible, He's not going to put you through anything that you can't handle.  And, I think that's what I fell back on in the moment on the train. I didn't necessarily at that second think 'God's got my back,' but I knew it. There was an opportunity to do something good. I believe those are the times where we're vessels to be used by Him, to do His work. And it was an honor to do something that good. 

SADLER:  I've been going to church all my life. My dad is a pastor. He became a pastor when I was older. We were a strong Baptist household. We went to church every Sunday, all the services. My family is Christian, faith-believing and I've grown up that way. And as far as on the train that day, God had His hand on us, because so many things could've went the other way for us.  And the fact that they went the way they did, it's divine intervention. It's that by definition. We knew He had His hand on us, because of the calm that we had as we were falling into our different roles that day - looking back on it in hindsight. That calm, I know where that comes from now that I've had a chance to evaluate that day. And I'm thankful that He had His hand on us that day. 

SKARLATOS: I grew up next to Spencer's family. We went to the same church for the longest time. We all met in a Christian school. I've been to church pretty much ever since I can remember.  If you look at the statistics of everything that happened, the odds of being in a terrorist attack are astronomical, the odds of surviving it, the odds of surviving it and being the ones that stopped it. There's so many little circumstances. The odds of our exact situation happening to us are too astronomical to believe that it was purely chance, especially when you look at the fact that we were thinking about staying in Amsterdam another day and we didn't. The fact that we moved seats from coach to first class. So many different little things that are hard for even us to remember - all the different circumstances that put us there in that exact time and place. But to me it's too coincidental to be chance. God had a hand in it, because we shouldn't be here today to be honest.

How did your faith influence your actions on the train? What prompted you to act so heroically in the face of eminent danger?

SADLER:    We were vessels being used. I don't even know how I got the first aid kit, but somehow it was in my hands. Alek was doing his thing clearing the car. Spencer saw somebody was bleeding and crawled over there. When did we think of that? We didn't think. We were just being used. 

STONE:    How well everything fell into place, you would think we rehearsed it. It was pretty much like we took over the train. I never felt more calm in my entire life. I knew exactly what we should do in that moment. It almost felt like someone pushed me towards it. I knew in my mind I had to go, and something greater stood me up. I think that's why they're still confused about how I got up so fast. I don't know how I got up so fast either. I'm pretty slow!  

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What was your experience like filming "15:17 to Paris," and reliving those tense moments on the train?

STONE:   It was pretty crazy when we did the scene of Mark bleeding out. That was the only time I really felt like I had a true flashback, because everything was the same. It was the same amount of blood, same clothes. That was probably the most memorable part on the train for me. 

SKARLATOS: It definitely made it easier to get back into character. You have to remember how it was on the actual day. And, I don't know about the other guys, but it would trigger an adrenaline rush in me and it make it easier to feel the same emotions that we actually felt the day on the train. 

SADLER:  It shows how much the details matter, like same clothes, same people, train attendants, everything. That made it all feel authentic. 

What do you hope viewers will take away from the film?

SADLER:   I want them to take exactly what it is. The fact that we're three ordinary guys that were faced with an extraordinary, crazy situation. And the reason why we acted the way we did that day is because of our friendship - the back-story matters. And then take away that they can, as people, a regular person, do something great, too. To feel like things are possible that they previously didn't think were possible. 

STONE:  I want them to take away that in our story, we thought we had no chance at all. I thought I was going to die. We're all regular people. We're very regular guys.

How has your experience on the train/filming the movie impacted your lives moving forward? Has it changed the way you live, or taught you any particular lessons?

SKARLATOS: I think making the film taught us a lot about ourselves. Then working through the process ourselves, we discovered a lot of things about ourselves, about our friendship, how we interact. And, for me I learned from the movie not to be afraid to try new things in life.

It cured a lot of my fears, even of public speaking. You know, if I can survive a terrorist attack, when the next challenge in life comes, it's nothing in comparison.

STONE:    We definitely learned a lot about each other throughout the last two years in general. We've known each other our entire lives, but, we've spent most our lives apart, going off on our own paths and different avenues. We, in a sense, got to learn more about each other as adults and through this experience. We knew each other, but now we really know each other. And we're bonded forever through all of our experiences.

SADLER:    For me it was the first time in my life I finally felt like I was on track. I was going to go into my senior year at college and I didn't know after that year was over what I was going to do next.

And then once the attack happened and everything else that's happened in the last two years, and the fact that the movie happened, the way it's all lined up, I feel like I'm finally on the track that I'm supposed to be on. So, I don't know what comes next, but I'm on the plan that's been set for me. That's a good feeling, I have confidence in knowing I'm going in the right direction.