"Mission complete", Jim McGrath tweeted along with the photo.
The dog - who has his own Instagram account - was named after the airline pilot Chesley "Sully" Sullenberger, who in 2009 landed a passenger jet on the Hudson River, saving all of the 150 people on board.
Sully will accompany Bush's casket on the Monday flight from Houston to Maryland, CNN reported, citing a source familiar with the plans. Sully will reportedly return to America's VetDogs in NY to serve in the Walter Reed National Military Medical Center's Facility Dog Program.
The report noted that Sully can perform a number of commands, including answering the phone and fetching specific items.
"He kept us flying high and challenged us to fly higher still, and he did it with modesty and kindness that would've been surprising in someone one-tenth as tough and accomplished as he was", McConnell said.
Wreaths were placed at the casket by congressional leaders from both parties, as the Bush family, including former President George W. Bush looked on. "Could not be more grateful, especially for their commitment to our veterans", Bush said on Twitter about the dog in June. The train will take about 2½ hours to travel roughly 70 miles to the city of College Station, home to Bush's presidential library at Texas A&M University.
"I think he was one of the kindest, most generous men", said Marge Frazier, who visited the downtown statue on Sunday while showing friends from California around. He died in Texas, his home state, late Friday at the age of 94 after several years of failing health.
In Washington, Bush will lie in state in the rotunda of the U.S. Capitol from Monday at 7:30 p.m. EST until Wednesday at 8:45 a.m. EST. An invitation-only funeral service is set for Wednesday at Washington National Cathedral. President Donald Trump and first lady Melania Trump are scheduled to attend.
Dukakis, 85, blames himself for his election loss as the Democratic nominee, saying he didn't respond aggressively to a Bush campaign ad featuring a convicted murderer named Willie Horton who raped a woman and stabbed her partner while out of prison on a MA furlough program.
The 41st President will be carried to his final rest wearing socks that pay tribute to his lifetime of service, starting as an 18 year-old naval aviator in war.