A 50-year-old man hiking alone in Foothills Park at about 4 p.m. on Saturday was knocked down from behind by a mountain lion, tumbled down a 15-foot slope and struck a tree. He then saw the lion tumble down the same slope into Los Trancos Creek.
The big cat then scampered away, according to Palo Alto Police Agent Dan Ryan. The hiker had "scrapes and bruises" but did not require medical attention, Ryan said.
There was also a possible mountain lion sighting in the adjacent Pearson-Arastradero Preserve.
As a precaution, the city temporarily closed both Foothills Park and the preserve to visitors.
Ryan said a tracker will be brought in to try to find the lion.
The attack on the hiker was the first confirmed mountain lion attack on a human in Palo Alto, Ryan said.
Officials from the California Department of Fish and Game and the U.S. Department of Fish and Wildlife were brought to assist city park rangers. They believe the mountain lion may have been an adolescent that "misjudged his prey."