Columbia, SC (WLTX) - One couple is mourning after their dog was mistakenly put down by the City of Columbia animal shelter.

Jeff Stahl and Abby Frotten are engaged to be married and they took care of their German Shepherd, Tyson, for nearly four years.

"He was everything to us. I mean we did everything together," said Stahl.

"He saved my life more than one time with seizures and stuff. I mean he wasn't a service dog but he was mine and he helped me and he loved me," tearfully said Frotten.

Last week, Tyson escaped from the backyard and the couple couldn't find their dog. They later learned that their dog was being held at the City of Columbia animal shelter. Stahl and Frotten needed to pay fees for their dog being on the loose and for him not being registered with Richland County.

After a couple of days collecting the money, they called the shelter to say they were coming to pick up Tyson. An hour later, they got the news.

"He was accidentally euthanized. He was mistaken for another dog and that right there is unacceptable," said Stahl.

The City of Columbia Public Works says this was a mistake.

"Clearly it was a matter of human error. When our officer went through to pick up the animals to be euthanized, he picked up the wrong animal of the wrong pen," said Robert Anderson with the city.

Although they have procedures in place, they are planning to make sure that this doesn't happen again.

"We go back through and look through our policies and procedures. We make sure that we are doing the right thing in our shelter and reiterate to our people to make sure that they double check everything we do. It's an unfortunate situation and we're sorry that it happened.," said Anderson.

Stahl and Frotten are devastating and trying to figure out what to do next.

"I know that I lost my son. I lost him. He's gone. He's gotten me through everything. I don't know what the next step is other than justice for him," said Frotten.

The couple have not decided yet if they will take legal action. Their main concern is to prevent this from happening again to any other pet.