Snapping at the pizza carrier was a death sentence for Zion.
The rowdy Lab mix with big feet and soulful eyes was supposed to be going home Thursday after 10 days in quarantine at the McKamey Animal Care and Adoption Center.
Instead, through an unexplained mix-up, Zion was euthanized.
His owner, Matt Sadler, is heartbroken.
He said he came to the shelter Thursday morning expecting a joyful reunion, but learned instead from Executive Director Karen Walsh that his pet was dead -- euthanized that very morning before the shelter opened.
"I was hysterical -- I had talked to at least five people about my dog. She said nobody put in the file I was coming to pick him up or showed any concern about him," Sadler said.
"They never once tried to call before they euthanized my dog. ... They gave me no chance to come get Zion. They just put him down."
Walsh said she and everyone else at the shelter are saddened at the pet's wrongful death.
"Understandably [Sadler's] horribly upset. Every staff member insisted they wanted to speak to him when he came in [Thursday] so he could see how devastated they were," Walsh said.
"In our business, mistakes cost lives, and that's not an excuse," she said.
Sadler, 25, a geology major at the University of Tennessee at Chattanooga, adopted Zion from a shelter as a 6-week-old pup. He said his girlfriend noticed a furry spot on the dog's back -- he thinks Zion may have had some Rhodesian ridgeback in him -- that "kind of came to a mohawk."
"My eyebrow does something like that. She said, 'Y'all are perfect for each other,'" Sadler said.
He chose the name Zion because he wanted "a really strong name."
"He turned out to be a really strong, protective dog, but he was really sweet. My dad used to call him Sugar Bear. He could always tell when I was upset because he'd always come sit by me. Something like that you can never get back," Sadler said.
"I had every intention this dog was going to be the one that my kids grew up with," he said.
Zion, who was going on 4 years old, lived with Sadler, two roommates and a boxer mix, Comrade, in an East Brainerd home.
When the dog nipped at a pizza delivery carrier and Sadler couldn't come up with a current rabies certificate, the city's animal control ordered the dog quarantined for 10 days.
Walsh said the shelter has about five "bite quarantined" dogs at any given time, among the 8,400 or so animals it takes in every year.
"It's a regular thing for us to quarantine animals. The majority are never reclaimed," Walsh said.
In pictures Sadler sent to the Times Free Press, Zion isn't wearing a collar. Walsh said he didn't have any kind of ID at the shelter, either.
But it shouldn't have cost Zion's life, she agreed.
"It was a mix-up between three different employees that should never have happened. And it did," Walsh said. "But I don't think one mistake erases all the good work our employees do. Our people love animals; that's why we're here."