Einstein Burns, the dog that played Cain in the rock star western epic Red Dead Redemption 2, has passed away. The news of Einstein's passing was shared on Instagram by his owner and colleague, RDR2 animator Jason Barnes.

"Einstein was truly one-of-a-kind. From the moment we met, it was clear that we were deeply bonded and destined to share countless adventures together."

"Our time together has come to an end, but your memories will live on forever. Red Dead Redemption 2 may immortalize you as Cain, but it is the memories we created together that will truly preserve your spirit. The lessons you taught me about loyalty, love, and living life to the fullest will never be forgotten."

Barnes told PC Gamer that he first met Einstein, then named Hero, at a shelter when he was still a puppy. Inspired by "Cowboy Bebop" and "Back to the Future," he renamed Einstein Ein and trained him as a service dog.

Einstein became involved in the production of Red Dead Redemption 2 after Barnes was promoted from Rockstar's San Diego office to the New York office. The move was a "big adjustment" for both men, but he was able to bring Einstein into the office every day, where he became known as "the best dog." According to Burns, his only problem was that he would occasionally "gush" when he saw certain members of the team, especially ingame cinematographer Luke Howard."

When Barnes began working on the set of RDR2 motion capture on Long Island, Einstein often accompanied him on the drives. His turn as Cain began as a fitting to test the dog's mocap suit, but "by this point he was known to all the actors and his service training made him a perfect mocap dog, accustomed to sitting and waiting patiently."

The dog's role as Cain was a "very good one.

"It started with a few tests, and the next thing I knew I was cast as Cain," Burns says. 'I have fond memories of working with him on set as his trainer. We did some clever stage offsets [shooting angles] and such to film the stunt where Mica kicks Cain and Mica chases Cain away. He was crazy about lasers, so we often used lasers to make him run in a particular direction.

"He was often glued to every shot and did a lot of basic dog stuff movement mocap, but his mocap time was mainly focused on Cain's moments and acting. He was so good. The actors were amazed."

And indeed, he is listed in the credits of RDR2:

Barnes' Instagram post drew reminiscences from other members of the RDR2 development team. He wrote: "I remember how super welcoming and comfortable you and Einstein made me feel during my first few weeks at Rockstar.

"Einstein is a really special dog and I am so grateful to have shared some special mocap time with him. He wore that suit so well."

"He will be missed," added a third. 'I loved working with you both.

InXile Entertainment, where Barnes is now animation director, also paid tribute to Einstein and his mo-cap abilities.

Barnes said Einstein "definitely" would have lived into his 20s, but cancer set in. 'When I used to take him to the dog park and let him play, everybody thought he was a puppy,' he said. Until about two months before he died, he was chasing and playing with the younger dogs." Einstein died at the age of 13.