Rocky's former owner kept him outside, and the frail, 17-year-old dog just kept running away.

He would turn up at Anne Arundel County Animal Control (AACAC) in Maryland. When he turned up again in December 2015, he had no idea he was about to get a whole new life.

Senior dog saved from shelter in MarylandBeth Clark

Beth and Michael Clark were just dropping off some donations at the animal shelter when Beth asked if they could take a quick look at the dogs up for adoption.

When they saw Rocky, they just couldn't leave without him.

"He just looked so sad," Beth told The Dodo.

But Rocky wasn't sad for long.

17-year-old dog getting adopted from shelterRocky was 17-years-old when a nice young couple adopted him from the shelter.FAACAC

The senior dog was adopted into his new loving home just in time for Christmas. He was immediately part of the family.

"Everyone loved the story of a young Fort Meade couple who came to AACAC right before Christmas 2015 just to drop off donations, but ending up adopting a frail, 17-year-old dog named Rocky," Chris Collins, of Friends of AACAC (FAACAC), wrote.

Senior shelter dog playing in the snowBeth Clark

Senior shelter dog napping with his rescuerBeth Clark

The young couple was so happy to have this new family member with them to celebrate the holidays β€” and Rocky was so happy to have a family.

"Rocky thrived in his new home," Collins wrote.

Senior shelter dog spending Christmas at his new homeBeth Clark

Senior shelter dog saved in time for ChristmasBeth Clark

When Beth and Michael learned they were expecting a child, Rocky even helped the happy couple announce their good news.

And Rocky was with Beth all along the way. "When I started showing, he was a lot more attached to me," Beth said.

Senior dog helps his parents announce they're expecting a babyBeth Clark

Even though Rocky had really started slowing down, he still showed how much he loved his family.

Senior shelter dog with his pregnant ownerBeth Clark

Last week, in the early hours of Wednesday morning, Beth had a daughter. The couple named her Hazel.

On Thursday evening, the family came home from the hospital, and Rocky was there to meet his tiny little sister. He looked at her and sniffed her. But it was clear to Beth and Michael that something was wrong. He was very weak and his eyes were glassy.

Senior shelter dog meets his new baby sister before passing awayBeth Clark

Just a few hours later, Rocky, well over 18 years old, quietly passed away.

"We're still adjusting to Rocky not being here," Beth said. "I'm just really glad he was there when we got home."

"Dear Hazel: Someday your mom and dad will tell you all about your first dog, Rocky," FAACAC wrote in a little letter to the Clarks' new daughter, after learning that Rocky had passed away. "Late Thursday night he peacefully left the world that you just entered."

Senior shelter dog meets his new baby sister before passing awayBeth Clark

Just before Rocky died, Beth and Michael snapped a few photos of Hazel and Rocky together. "Someday, they will show you that picture, and tell you how wonderful and how loved your first dog was, even though your lives only overlapped so very briefly," FAACAC wrote.

"I hope our story helps other people decide to adopt senior dogs," Beth added.

To help FAACAC rescue dogs like Rocky, you can make a donation.