Every couple of years warnings are posted on the trail near my home of a mountain lion sighting. The trail follows a creek up into the lower Santa Cruz Mountains, so there's lots of places wildlife could do their thing. Because the relevant section allows walking from from Los Gatos to Campbell and passes by Los Gatos High School and through three parks it's a pretty heavily used trail.
Similarly, there are mountain lion encounters with runners and hikers in Sierra foothills, including a couple of killings.