He had a collection of colorful socks and often tweeted about them.
The body of former President George H.W. Bush will lie in state in the U.S. Capitol on Monday as his family and Americans mourn the loss of the 41st U.S. president.
Jim McGrath, Bush's spokesman, posted an image of Sully next to Bush's casket on Sunday along with the caption, "Mission complete".
According to America's VetDogs.org, the specially-trained service dog was specifically matched to provide support and companionship to the late President Bush in his daily activities.
Wednesday, Dec. 5, 11 a.m. His body will be transported by motorcade to St. Martin's Episcopal Church, where he and his wife regularly worshipped.
President Donald Trump has declared Wednesday, Dec. 6, a Day of National Mourning.
David J. Phillip Pool AP
It remains to be seen if Sully will also return to Texas with the Bush family, Rubenstein said, as plans have been hard to arrange in the midst of the funeral arrangements.
The locomotive has been painted the colors of the Air Force One plane used during Bush's presidency and bears the number "4141" in honor of the 41st president.
The elder Pence said his son had graduated from Naval aviator training - which he said included making a "tailhook" landing on the U.S.S. George H.W. Bush.
The train is scheduled to arrive in College Station on Thursday around 3:45 p.m. CST.
Former President George H.W. Bush's service dog lies in front of his casket in Houston on Sunday.
Bush married Barbara Pierce in 1945.