A guide dog died after being left in an overheated van for hours at a training facility in Smithtown, according to the dog's owner.

Michelle Krupa, of Medford, says her guide dog Milton meant a lot to her.

"They're more than just a pet, they're more than a tool," Krupa says. "They become your guardian angels."

Krupa suffers from a rare genetic disease called Usher syndrome, which affects her vision and hearing.

Milton helped her live independently, protected her and was her best friend.

"He knew when I was upset, he knew when I needed him, he sat next to me under my feet," Krupa says. "He was always with me."

The 3-year-old black Lab was dropped off at the Guide Dog Foundation in Smithtown for additional training about two weeks ago.

Krupa says workers there accidentally left him inside a van in the parking lot from 10 a.m. until 3:30 p.m.

The temperature that day was in the low-90s, and Milton had died by the time he was found.

In a statement, the Guide Dog Foundation wrote, "It is with sadness we can confirm that a guide dog from our program passed away on Friday, July 22, 2022, while in our care at the Smithtown campus...We are conducting a thorough review of the events leading to this tragedy."

A spokesperson for the Guide Dog Foundation says the incident has been tough for them as well - so they are offering mental health counseling to their workers.

Once the investigation is finished, the organization says it will take steps to prevent something like this from happening again.

Krupa says she will eventually need a new guide dog to help her get around, but none will replace the one she lost.

"It's not going to be my Milton," Krupa says.