A heartbreaking image shows George HW Bush's service dog lying next to the 41st US President's casket in Houston.
Sully, a specially trained yellow Labrador Retriever, was pictured lying mournfully next to Mr Bush's flag-draped coffin.
It was shared to the dog's Instagram account on Sunday with the caption: "Mission complete."
The two-year-old dog was placed with the former president in June by America's VetDogs to provide support and companionship to Mr Bush after former first lady Barbara Bush died earlier this year.
Sully is named after former airline pilot Chesley “Sully” Sullenberger III, who became famous for landing a damaged passenger jet on the Hudson River in 2009.
The dog will accompany the president's casket on his flight to Washington, DC, CNN reported.
A highly trained dog, Sully will now go back into service to help other veterans, former President George W Bush wrote on Instagram.
He is going to Walter Reed National Military Medical Center, Mr Bush added.
"As much as our family is going to miss this dog, we're comforted to know he'll bring the same joy to his new home, Walter Reed, that be brought to 41," Mr Bush wrote.
His official Twitter account posted an image of Sully alongside his father and another former President, Bill Clinton, on June 25 after the dog's arrival at his new home.
The tweet read: "A great joy to welcome home the newest member of our family, "Sully," a beautiful - and beautifully trained - lab from America’s VetDogs.
"Could not be more grateful, especially for their commitment to our veterans."
America’s VetDogs is a New York-based nonprofit group which provides service dogs to veterans.
