The incident occurred about 5 a.m. June 15, which was the last day of school, and may have been a senior prank gone wrong, according to the San Diego County Sheriff's Department.

A security guard reported seeing a male of about 5 feet 11 inches tall and weighing 180 pounds in a livestock pen with the two Tennessee fainting goats inside.

The male ran away when the guard shined a flashlight on him, authorities said.

The guard removed the duct tape from the goats' snouts but for one of the animals, it was too late.

A necropsy -- the animal equivalent of an autopsy -- revealed that the goat died from suffocation, authorities said.

San Diego County Crime Stoppers is offering a reward of up to $1,000 for information that leads to an arrest in the case.

An additional $2,000 reward is being offered by the San Diego Animal Advocates.

Anyone with information about the case is being asked to contact Sheriff's Detective Jim Pucillo at (760) 451-3100. Tipsters wishing to remain anonymous can contact Crime Stoppers at (888) 580-8477 or at www.sdcrimestoppers.com.