It's a pet owners worst nightmare -- a lost animal winds up in a shelter and killed in under 24 hours. That's the sad reality one family lived Thanksgiving weekend - all caught on camera. and now serving as a cautionary tale.

On Nov. 30, a pet owner went frantically looking for his 16-year-old mastiff Lila, only to discover it was killed hours after turning up in a shelter. Lila was found in a Staten Island park early Saturday morning and brought to the Staten Island Animal Care Center. That same day the dog was sent to the Manhattan location where it was put down.

In a video obtained by News 12, the owner is seen and heard telling Animal Care Center of NYC employees "it's not even 24 hours," asking why his animal was killed. The two-minute video shows the owner arguing with employees that his dog was a rescue he got from the ACC at three months old and micro-chipped. The employee in the video responded that the chip "had no phone number" but the owner immediately says "but there was an address correct?"

"Yes," employees admitted.

Erica Curtin filmed the entire confrontation and was stunned. "I cried a little bit and kept profusely apologizing to the owner," she told News 12. "It was kind of heartbreaking."

News 12 reached out to the ACC about Lila's case and received this statement:

"At ACC, it is our job to be an advocate for animals, especially in times of need and when they are suffering. Providing end of life services is a difficult, but essential part of animal welfare. Following an examination of Lila/Brodie, a veterinarian concluded that she was suffering and her quality of life was so poor that euthanasia was the only humane option," says Katy Hansen, Director of Communications at Animal Care Center of NYC.

But Lila isn't the first case of this with the ACC. This past September, a 16-year-old Shitzhu named Mr. Magoo was found in Queens, brought into the Brooklyn ACC and killed later that same day. His finder even told the shelter just hours before it happened he would adopt the dog and to call him before doing anything. In that case the owners also showed up the next morning only to learn their dog was put down.

Annemarie Lucas, a former humane officer and star of the Animal Planet show "Animal Cops," tells News 12 "everyone failed that dog."

"You have no idea if she (Lila) was under medical care, you have no idea how old she was; because you had no information. Why rush to kill the dog before speaking to the owner? Lila was chipped, maybe no phone number, but there was an address five minutes from the Staten Island shelter," she says.

Lucas says some shelters will deem older animals or animals with a compromised health as "un-adoptable," placing them on the fast-track for euthanasia. A grim reality, but something she admits she's heard happen a number of times in her long career as an animal cop.

According to New York State Law, shelters have authority to euthanize animals that are "suffering" but should hold unidentified strays for five days and identified strays for seven.