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 being led away by handlers after the fatal attack. Mikaela Bjorkma/KATU 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.…