TULSA, Oklahoma - Investigators are trying to figure out if three German Shepherd puppies died of natural causes or were killed.

The Tulsa Police officer who found the dogs tells me the animals didn't have gunshots or cuts but he says one puppy looked like it had been folded in half. Tulsa Animal Welfare says they don’t know yet if the puppies died from abuse.

A green barrel, a vacant apartment complex and three lifeless puppies wearing brightly colored harnesses is an image Tulsa Police Officer Luke Flanagan says he'll never forget.

"I have been doing this for about 8 years and this one was definitely…it was horrible," said Officer Flanagan.

Officer Flanagan was at Silverwood Apartments (a vacant complex) with police, searching for a man, who witnesses say had parked a stolen car on the property.

As Officer Flanagan turned the corner, he says he saw a dog hanging out of a green barrel.

"I was almost blown away when I saw it at first,” said Officer Flanagan, "As the officers went to tip over the tub unfortunately it was found that there were a total of three dogs that had been pushed down in there, dumped, wrapped inside of these blankets."

Tulsa Animal Welfare says they had a vet look over the puppies bodies and then sent the dogs to Oklahoma State University for a full necropsy.

"We don't know if there is animal abuse involved, they could have died of natural causes and someone simply didn't know how to properly dispose of the bodies," says Tulsa Animal Welfare Manager Jean Letcher.

If the lab results show that animal abuse caused the puppies to die they say they will try and find enough evidence to build a case.

"In a situation like this where these dogs obviously couldn't speak for themselves, it would be outstanding if we could get community support to have some type of tips to find out who is responsible for this,” said Officer Flanagan.

The Oklahoma Alliance for Animals told News On 6 they are paying for the puppies necropsies, they are also offering a $5,000 reward for information leading to an arrest in the case. Police are asking anyone who knows anything about these puppies, their owners or how they ended up at the apartment complex to call Crime Stoppers.

Full statement from The Oklahoma Alliance for Animals:

“OAA is offering a $5000 reward for information leading to the arrest and felony conviction of person(s) responsible for this felony crime of animal cruelty. OAA is also funding the three necropsies at the Oklahoma Animal Disease and Diagnostic Lab at OSU in Stillwater to support strong prosecution of the case. 

The Oklahoma Alliance of Animals strongly supports the work of law enforcement and prosecutors who enforce and prosecute animal cruelty and neglect cases. Animal cruelty cannot be tolerated.

There is no excuse for animal abuse. Research1 documents that were animal cruelty is found there are almost always other felony crimes. Enforcing the state felony law against animal cruelty must be a priority for law enforcement, and we are grateful that the Tulsa Police Department is accepting our support.