The 19-year-old was dressed down in a casual sweater, jeans, and hair band as he hung out with Zach, who was at the film fest to promote his new project Wish I Was Here, a movie he funded on Kickstarter.
But it wasn't such a laid back night for One Direction fans, who freaked out when they spotted their crush.
"A massive group of women and girls were literally running down the street from all sides, screaming his name, snapping photos, and swarming around him," a source tells In Touch, adding that Harry jumped in a car to try and make a hasty exit.
One good news for Harry fans, though: the singer, who has lately been linked to Kendall Jenner, was in town by himself. "It was like he was one of the Beatles," the source reports about the chaos around the pop star. After he got into the car, fans began jumping on top of it and causing a scene.
Across the street in the Columbia Sportswear lounge, Harry's new BFF Zach was witnessing the scene from the window and was growing very concerned for his friend. He was overheard saying "I hope Harry is OK" and appeared to be very worried about hs pal and looked like he was trying to text him.