Colorado Bride's Dying Dog Carried Down Aisle at Her Wedding: 'He Had the Biggest Smile on His Face'

Kelly O'Connell's dream Colorado wedding was made even more special by the appearance of her sick dog, Charlie, being carried down the aisle by her maid of honor.

The late 15-year-old black lab mix, who was diagnosed with a brain tumor five months prior to the ceremony, hobbled down the grassy aisle – but was unable to stand up and follow his owner after the ceremony began.

So, O'Connell's sister, Katie Lloyd, scooped Charlie up and proceeded down the walkway where she placed him in front of O'Connell and her new husband, James Garvin.

"I had just gotten married and everyone was congratulating us, but we ignored them and dropped to our knees and petted him and loved on him," O'Connell, 33, tells PEOPLE. "I kept saying, 'You made it buddy!' "

"He had the biggest smile on his face that he was there to see me get married. His body was failing him, but I could tell he was happy."

Charlie died nine days after Garvin and O'Connell tied the knot.

"I'm so happy he was able to be a part of my wedding," says O'Connell says of her beloved dog.

The touching images, which have since gone viral, were captured by Boulder-based wedding photographer Jen Dziuvenis.

O'Connell, a veterinarian, adopted Charlie after he was abandoned in a shopping cart outside a Buffalo, New York, grocery store in the middle of the winter.

"I was only 19 at the time and in veterinary technician school and wasn't looking to be a pet owner," she recalls. "But when I saw him I knew he was my dog and we'd always be together."

When O'Connell met Garvin, also a veterinarian, six years ago, her first thought was, "Will Charlie like him?"

"We had a long history of being single and on our own!" she says. "James also has two sons, so I needed to make sure everyone got along with Charlie. Turns out he adored the boys and they adored him."

The loving owner – who describes Charlie as "super high energy" – says the two ran together almost every day.

"He was my marathon training partner, he could run 20 miles with me, he absolutely loved it," says O'Connell. "We were on a run in April when he had his first seizure.

"Then they discovered the brain tumor."

O'Connell says it was extremely difficult to watch an energetic dog like Charlie go from constantly running around to not being able to walk.

"It broke my heart, he had five seizures the week before the wedding and we considered putting him down, but he seemed to get better, so we waited," she explains. "And it was worth it to see the happiness on his face that day. He wanted to be there and I'm glad he was."

A little over a week after O'Connell and Garvin said "I do," Charlie's condition worsened and the owners were forced to put him down.

"James' boys laid next to him on a pillow in his final moments," she says. "Charlie was so loved."

She adds, "I'll miss Charlie, he was my best friend. But he'll never be forgotten. And we'll always have the wedding photos to remember him by."