Tal Peleg, who was Senior Cinematics Animator on TLOU and Uncharted 4, and now Lead Cinematics Animator on Anthem, has been working on this on his personal time for the last 5 or so years. I gotta say it's really impressive! Even have a nice cameo in it in the end.
It's apparently a sequel to another short released in 2014:
It's apparently a sequel to another short released in 2014: