From sheer joy to unimaginable heartbreak.

That’s how the Bastidos’ family describes the ordeal they went through after bringing home a new Chihuahua puppy they named Mila.

“The puppy was really tiny and cute,” said Veronica Bastidos. “We were all excited right away.”

Bastido still gets emotional when talking about what happened to Mila.

“We didn't think about the stuff we see now, all the red flags,” Bastido told 12 News.

After first trying to find a dog to adopt at a local animal shelter, the family decided to look online.

That’s when they spotted a Craigslist ad selling Chihuahua puppies.

A few hours later, they met the seller outside of a north Phoenix apartment complex.

“He brought out the puppy and everything seemed legit,” Bastido said. “He even came out with a vaccine record.”

But within just a couple days, Mila got sick.

Which left Bastidos’ son,10-year-old Alonso, feeling helpless as the puppy's health quickly deteriorated.

“To see her suffer,” is what Alonso says was the hardest part.

“She was happy like a day ago and then all of a sudden she was sick and in pain,” he said.

The family rushed the tiny Chihuahua to the hospital,

But after spending close to $450 on IV's and medication, anything to save her, the family was left devastated.

"All night long she just became weaker and weaker and in the morning she started having seizures and that's when we lost her," Bastidos said.

Animal advocates believe Mila was likely the victim of what’s known as backyard breeding. You can find the ads for animals are all over the internet.

People selling puppies that many times aren’t vaccinated, given proper medical care and are kept in unsanitary conditions, which can lead to severe health problems.

"You won't see symptoms for a week or more sometimes and at that point you've already adopted the dog, the craigslist post is gone and now you have a dog with parvo that can cost up to $2200 to care for," said Michael Moreland from the Arizona Animal Welfare League.

As for the person who sold Mila, their phone number has since been disconnected.

"It's sad, it's very sad and I'm pretty sure that we're not the only ones that this has happened to," said Rosie Goolsby, Bastidos' mother.

The family is now hoping to warn others about the risks of buying a pet online.

She hopes other adopt and don't buy after hearing her story.

"I've never seen a living being suffer to death and that was the most traumatic part," said Bastidos.

The AAWL says because much of backyard breeding can be considered a hobby it is difficult to stop or even regulate.

They say the best way to stop inhumane breeding is to purchase from a reputable shelter or organization instead of buying online.