One afternoon in late July 2013, just weeks after his eleventh birthday, our black Lab, Kirby, wouldn’t move. All afternoon, he lay at the foot of the stairs with a pained, heavy look in his eye. That night, for the first time in family memory, he failed to make it to my son, Owen’s, room to sleep beside him. Instead, Kirby stayed on the cool bathroom floor, a place he rarely went, let alone slept.

Kirby’s intermittent bad days had started nearly a year earlier, when he struggled to make it up the stairs or couldn’t summon the energy to chase tennis balls. Yet, every time before, after a day or two of exhaustion, he’d always rally enough to resume playing in the yard with our kids, then eight-year-old Owen and five-year-old Maisy. So, on this day in July, confident that Kirby’s illness was temporary, my wife, Kara, decided to take him to the vet for his next exam.

Something was wrong, though. Kara labored mightily to get our slow, reluctant Lab into and out of the car. Kirby, never the kind of dog to voice displeasure, growled, groaned, and pulled on the leash before finally consenting.

At the vet’s office, Kara heard the words we had dreaded ever since we first fell in love with Kirby’s floppy black ears. The vet had found a large mass in Kirby’s stomach; our dog was in terrible pain, and the end was here. The vet said he shouldn’t even be moved again. Kara’s anguish bled into her voice when she called to tell me. She was coming to pick up me and the kids so we could all be with Kirby one last time.

When the four of us arrived back at the vet’s office, Kirby was lying inert on the sterile linoleum floor, his chest moving in ragged bursts. Each shallow breath was work. Owen and Maisy threw themselves onto him, wailing. Kirby mustered just enough energy to raise his chin and gently lick Maisy’s nose. Owen hugged Kirby’s neck, screaming his grief like a mother who had just lost her son—“No! No! No!”

The vet entered and knelt next to Kirby, holding a syringe loaded with a medicine that would take away his pain but also his life. Owen stayed put at Kirby’s side; he refused to allow his friend to depart alone. As the vet gently inserted the needle into a spot she had shaved on Kirby’s back leg, Owen announced to the room, and perhaps to the universe, “My face will be the last thing Kirby sees.”

Owen rested his nose against Kirby’s, locking eyes, and I watched my son as the light in his dog’s eyes went dim. All the while, Owen kept his arms around his pal’s head, his tears wetting the muzzle of the dead dog. I couldn’t take it. I took Maisy by the hand and left the room. I had known sadness would come, but I was surprised to feel a rush of anger at the thought that Kirby would never return. I headed outdoors with my daughter to feel the grass under my feet.

I’ll never forget Kirby’s death, but what I remember most about that day is what happened afterward, in that same room, between the boy and his departed dog. When Maisy and I came back inside, Kara was sitting with Owen while he petted and embraced Kirby and continued to cry. Owen knew that his best friend was gone, but he wasn’t ready to say good-bye. I watched as he quieted, stood, wiped his cheeks, and said to his mom, “I will be right back.”

Owen walked out to the lobby and returned with a dog treat and a paper cup he’d filled with water. Silently and purposefully, he knelt before Kirby’s body, placed the tiny dog bone on Kirby’s back, and, dipping his finger in the water, reverently made the sign of the cross on Kirby’s forehead. Then he lifted his hands to heaven like a priest at the altar, looked up, and whispered, “I love you, Kirby. Good-bye.”

That’s the image I can’t shake.