A Nevada husband returning home from work made a horrifying discovery when he found his wife had been mauled to death by their newly adopted dog.

Susan Sweeney, 58, was attacked by the 3-year-old rescue canine she and her husband, Patrick, had adopted from a Las Vegas animal shelter last month.

In the recently released 911 call from the grisly discovery, Patrick explained it was a mastiff and he put the dog in the backyard to avoid further contact with the animal.

The 911 operator hoped there may be some hope of saving Susan, to whom Patrick Sweeney had been married to for 26 years.

“Let's try to help her," the operator said. "Listen carefully. Lay her flat on her back and remove any pillows."

"She's chewed up, bud," the devastated husband said.

“Do you think she's beyond help?” he was asked.

“Yes,” he replied.

The 80-pound dog was a mix of two potentially aggressive types, the mastiff and Presa Canario.

“They are known to be aggressive dogs," Veterinarian Jeff Werber, who has no connection to the case, told Inside Edition. "They are excellent watchdogs, guard dogs, and they were bred for that. They are popular. People like them. But they can be aggressive."

Werber says a rescue dog may seem docile and friendly in a shelter, but the animal's attitude can change once it's in a new home.

“We may not have seen his true colors in the shelter,” he said.

The shelter claims it didn't have any information that would have lead them to believe the dog was unsafe, adding that the dog didn't raise any concerns while in their care.

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