Someone—possibly in Russia—apparently strapped a submachine gun on a ~$3,000 robot dog available from AliExpress. Vice points out that the gun is a Russian PP-19 Vityaz submachine gun made in Russia and that along with a Russian flag and other insignia seen in the video, the vehicle in the background is a Russian BDRM-2 armored car. From Vice:
Finally, there's the account the video originally appeared on. Before making its way to Twitter, the video of the dog was posted to the YouTube account of Alexander Atamov on March 22, 2022. Atamov is listed on his LinkedIn profile as the founder of "HOVERSURF" and his Facebook page lists him as living in Moscow. He posted a picture of the robot dog on March 21. According to Facebook's translation of his post, he called the dog "Skynet."
Of course, Ghost Robotics showed off their gun-wielding robot dog last year, just months after art collective MSCHF's "Spot's Rampage" installation featuring a robot dog outfitted with a paintball gun.