Goodbye, Bretagne. On Monday, a 16-year-old Golden Retriever, the last known living 9/11 search dog was euthanized at a veterinary clinic in Cypress, Houston.

As members of the Texas Task Force 1, Bretagne and her handler, Denise Corliss, responded to the terrorist attack that brought down the World Trade Center during the Sept. 11, 2001 terrorist attack. The partners spent 10 days in search for human remains amidst the wreckage.

Apart from helping in the search, Bretagne also served as a therapy dog and provided comfort to the exhausted police and firefighters during the 12-hour daily shifts.

Corliss said that when task force team arrived at the 9/11 site, they could not believe the magnitude of what happened. When Corliss looked down at Bretagne, the search dog "seemed stoic and ready to work." At this time, Bretagne was only 2 years old.

Last September, Bretagne celebrated her sweet 16th birthday. Dog-themed content site BarkPost tagged team with 1 Hotel to celebrate the heroic dog's day in New York City.

The much-loved search dog was given the hero treatment that included a limo ride to the airport, a stay at the 1 Hotel suite overlooking Central Park, a vintage cab ride and a trip to Times Square where a personalized billboard displayed a birthday greeting for Bretagne.

Hudson River Parks also presented the 9/11 search dog with a dog version of the "Key to the City." Towards the end of the day, Bretagne's former Texas Task Force 1 teammates greeted her with a surprise party. The event was featured in BarkPost's ongoing "Dog's Best Day."

"It was really surprising and very touching to see how many people were involved and excited about her coming back to New York. Of course, it's not just about Bretagne. It's about the love and support that New York showed for those who responded to 9/11. She's kind of a symbol of that," Corliss added.

When Bretagne turned 9, she retired from her active duties at the Force. Apart from serving at Ground Zero, the 9/11 search dog was also part of the search and rescue team that responded when Hurricane Katrina hit New Orleans in 2005.