They’re in the dog house. 

A pup showcased by the Humane Society during an adoption event at a marathon in Washington state killed an attendee’s beloved dog — devastating the pet owner and sparking outrage.

“His owner was sobbing on the ground, holding [the dead dog] while people surrounded him. It was really heartbreaking to see,” Alexis Drugge, who saw the aftermath of the fatal mauling, told KOMO news.

The attacking dog, Dallas, was wearing an “Adopt me” vest near the finish line of the Tacoma City Marathon at Point Defiance Park on May 3, when he pounced on the other pooch while in the care of a volunteer, according to the local station.

Dallas, whose breed was not reported, was later classified as dangerous and euthanized, according to the Humane Society.

“The Tacoma Humane Society set this handler and rescue dog up for failure,” Dugge fumed. “It is completely unacceptable that they were at this event.”

Photos posted online showed a bystander comforting the traumatized volunteer while others helped restrain the dog, according to pugetpress.com

Dallas had been adopted from the agency two days earlier then returned for unclear reasons, according to pugetpress.com

The Humane Society said Thursday it is “deeply sorry for the harm” and is reviewing policies regarding how dogs are handled at off-site events.

“We take full responsibility for understanding how this happened and for addressing any deficiencies in our processes, oversight, or safeguards,” the agency said in a statement.“The safety of the animals entrusted to us and the broader community must come first, and in this instance, we did not meet that standard.”

No other details about the dog that was killed or its owner had been released Thursday.