It seems like one of the Separatist leaders, Girkin — a Russian GRU (military intelligence / subversion) officer with experience in Chechnya, momentarily claimed credit for shooting down a Ukrainian plane before realizing it was a passenger plane.

https://www.facebook.com/photo.php?fbid=848428975168507&set=a.314896515188425.88344.100000042388077&type=1&theater

It’s definitely true that the plane was shot down. It’s also definitely true that 3-5 Ukrainian military planes were shot down in the same area. It’s also guaranteed that each side is going to accuse the other of shooting down the airliner.