Ryan told MTV News: "I was in Amsterdam and I was probably about 20. People can wander around a little affected there, and this guy was on something funny and he just came at me.
"It was all a blur. I ended up in this quick little brawl and then it was over. Then the next thing I knew the police were escorting me to the train station and asking me to leave.
"Not because I was in trouble, but because they thought, 'If this guy sees you again, he's going to stab you.' I was escorted off the city limits."
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For 'Safe House', Ryan got to star opposite Denzel Washington, playing a character who has to prevent the escape or kidnapping of a dangerous rogue CIA agent from a safe house, and he said the film provides an interesting character study.
He added: "You have two characters that are obviously diametrically opposed but they're sort of marching toward one another.
"My character is an idealist, Denzel's is basically a sociopath. They're taking slow, steady steps toward each other, and by the end they're kind of integrating.
"Denzel Washington, who is one of the greatest living actors today, and director Daniel Espinosa is a young guy with a fresh take on the genre."meat either, so we just sort of sat there and thought about it."