SAN JOSE, CA (KRON) – Four miniature horses and a Sicilian donkey were mauled to death by dogs at San Jose’s Happy Hollow Park and Zoo, according to a statement on the zoo’s website.

Zoo officials say one horse was killed after closing Jan. 14. Maintenance crews arrived the next day to find Sweet William dead in his pen.

On Jan. 20 workers arrived to find Maybelline the donkey and the remaining horses, Luna, Cayenne, Spice Girl, dead inside the grazing pen.

Officials suspect the dogs dug under fencing to get inside.

One dog, a Belgian Malinois, was found at the zoo and the second dog was captured outside the zoo.,

A park spokeswoman says a third dog, a chihuahua, is still at large but is not believed to be a threat to anyone.

Zoo director Valerie Riegel says staff is heartbroken.