YOSEMITE NATIONAL PARK, Calif. (AP) _ A man sliding down a granite riverbed plunged over a waterfall and 1,400 feet to his death, a National Park Service official said Monday.

John Eric Ofner, 20, of Santa Barbara, was sliding in the water near the Upper Yosemite Falls on Sunday morning, NPS spokeswoman Mallory Smith said.

Witnesses said Ofner did not shout or appear to realize what was happening when he went over, Ms. Smith said.

Warning signs advising visitors to stay out of the water were posted at the time of the accident, she said.

Ofner and two friends had hiked to the top of the falls on Saturday and camped there overnight, Ms. Smith said.

The Upper Yosemite Falls forms part of a 2,405-foot waterfall descent that includes a set of cascades and Lower Yosemite Falls.