At least three dogs are dead and 12 more are missing after someone broke into the Riverside County animal shelter in Jurupa Valley and opened up their kennels, officials said.

The disturbing crime prompted five local organizations to offer a $20,000 reward for information that leads to an arrest and conviction.

UPDATE: Fourth dog found dead Monday; seven still missing

Riverside County Department of Animal Services spokesman John Welsh said a man in dark clothing can be seen on surveillance footage breaking locks to release 22 dogs from their kennels sometime late Saturday or early Sunday.

Two dogs – a Yorkshire terrier and a Chihuahua – were found dead in a kennel area with “blood spatter everywhere” when shelter employees arrived at 6:30 a.m., Welsh said. What exactly happened to them is still under investigation, but the initial exam indicated the injures were not caused by another animal, Welsh said.

Seven more dogs were running loose in the shelter, apparently uninjured.

Initially, 13 dogs were unaccounted for. One, a German shepherd, was discovered to have been hit by a car and killed. The shelter is at at 6851 Van Buren Boulevard, on a busy stretch of road just south of Limonite Avenue.

“This is extremely upsetting for us,” Welsh said. “We’re in the business of trying to save lives, we’re in the business of getting animals back to their rightful owners. … Our team was devastated.”

The Riverside County Sheriff’s Department is investigating the incident as a trespassing and animal cruelty case. Investigators have not publicly released surveillance images.

Anyone with information about the break-in at the county shelter may call investigators at 951-776-1099 or go to RiversideSheriff.org and click on “Crime Tips.”

Animal Solutions Konnections (ASK) and Shelter Transport Animal Rescue Team (START), which work with the county shelter to place stray or unwanted animals in new homes, put up $5,000 each for the reward. Three more organizations donated another $10,000 total through START, Welsh said.

Those who are interested in donating to the reward can contact Animal Solutions Konnections at 951-777-5341.

The dogs that were let loose had all been in the shelter’s stray kennel area. In addition to strays, the area holds aggressive dogs that have come to the shelter for observation and dogs that are suspected of being neglected.

“All the dogs in that area are animals who are waiting for their owners to show up,” Welsh said.

In the area where the two dogs’ bodies were found, blood was splattered more than three feet off the ground, Welsh said.

The county’s chief veterinarian, who was called in to determine whether the dogs were killed by a person or attacked by larger dogs, said the injuries “do not appear to be consistent with bite wounds,” Welsh said.

“We don’t know exactly what caused that, but we don’t suspect an animal,” he said. The final determination will be made once a necropsy, or animal autopsy, is conducted.

Welsh said he has not yet discussed bolstering security around the animal shelter with anyone.

“But that’s more than likely going to be a topic of discussion tomorrow,” he said.

Staff writer Alex Groves contributed to this report.