Coyotes disappeared from the city after the 1906 earthquake. They appear to have returned sometime in the past decade via the south peninsula. Recently a coyote was tracked with an electronic device, revealing that it traveled to Daly City and back in a single day (a trip that is agonizingly slow for commuters).
Over the weekend coyotes attacked a Rhodesian ridgeback, a large dog bred to hunt lions, in the park. To go after such a formidable opponent suggests the coyotes were protecting a den.
I have heard that city officials have killed the coyotes that attacked the dog, though I have yet to see an official report to that effect.
UPDATE: Yep, the shootings have been confirmed.