Rishi Bhatt donned a blue helmet as he prepared to slide down a zip line across the Baisaran Valley in Kashmir, a “mini Switzerland” where hundreds of tourists from India were enjoying a sunny April afternoon. Holding the rope in one hand and his smartphone in the other, he took off from the platform as the camera began recording.

Video filmed by Mr. Bhatt and verified by The New York Times shows panic unfolding as militants can be heard opening fire on tourists, killing at least two dozen people. His smile and shouts of glee are a jarring juxtaposition to the terrorist attack happening below him.

As Mr. Bhatt, who was visiting with his family from Ahmedabad, in the western Indian state of Gujarat, starts his ride down the zip line, the camera pans across an open meadow. Crowds of people are gathered around what appear to be yellow and blue tents next to a tall structure, which serves as the entrance to the valley. Others are taking a stroll or picnicking on the grass, out in the open to enjoy the spring sunshine.