MILLBRAE (KPIX 5) — The San Mateo County Sheriff’s Office on Thursday confirmed that a group of chickens killed at a Millbrae preschool over the weekend were killed by a dog.

Authorities have been investigating the disturbing case of vandalism since school administrators reported it on Sunday.

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“Some time between Saturday and Sunday morning, someone came in and tortured our chickens, and laid them out,” said Brigidan Bogni-Rodriguez, the director at the school.

At 10 a.m. Sunday morning, one of the teachers discovered the chicken coop and the rabbit hutch had been opened. A burglar had apparently ransacked the coop, which is next to the playground.

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School officials said it appeared the intruder killed all five chickens, slicing them open with a sharp object. Nothing in the school was stolen.

However, the San Mateo County Sheriff posted on the department’s Twitter account Thursday that the chickens had been killed by a dog. No mention is made of the birds being mutilated or killed by human hands. The post says the sheriff’s office will continue to provide support to the school.

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Because the post still referred to the incident as a case of vandalism, the investigation into that aspect likely remains open.