In Yosemite National Park on Tuesday, three hikers went missing when they were swept over a cliff by a waterfall. They are presumed dead.

The victims climbed over a barricade to get a better look at the powerful Vernal Falls and to pose for pictures when rushing water pulled them off of their feet. They fell about 300 feet to the rocky pool below, according to witnesses.

One of them slipped, and there was a chain-reaction as the other two tried to save the person who slipped, park spokesman Scott Gediman told the Fresno Bee newspaper.

Park rangers are currently searching for the bodies of Hormiz David, 22, Ramina Badal, 21, and Ninos Yacoub, 27. The hikers were from Stanislaus County in California and on a day trip to the park.

Vernal Falls is surrounded by a metal guard rail and warning signs. The group is said to have stood in the water about 25 feet from the edge of the fall.