He had a rope embedded in his neck when he was found in the Sunnyside area. Someone also shot him with a pellet gun.
READ MORE: Pup found with pellets in his neck released from hospital
"He moved, but very slowly. He did not have personality. His head was so swollen and so heavy," said veterinarian Dr. Lisa Howe.
Just a week after surgery, he's like a brand new dog.
"It's wonderful to see him blossom and not be afraid of people despite what could've happened to him," said veterinarian Dr. Daniel Eckman.
After having most of the band around his neck removed, the swelling in his head has been greatly reduced. He still has one surgery to go to remove the rest.
Doctors expect him to make a full recovery and then be available for adoption.
Marina Harrison works at the animal hospital and decided to take Gus home to foster him while he heals.
"He gets along great with my dogs. They all interact well and go outside together," she said.
Now, possibly for the first time in his short life, Gus is getting love, having fun and getting to be a normal puppy.
"He is starting to light up the room. Everybody loves him and he loves everybody despite his hard early months," Howe said.
A lesson of resilience and forgiveness.
"I'm constantly surprised at the number of animals that are just so forgiving; their tenacity and their ability to brush it off," Harrison said.
Gus serves as a reminder that while people have a great capacity for cruelty, it's no match for their capability for compassion.
Follow Steven Romo on Twitter and Facebook.