This particular screenshot seems highly suspicious to me. I can't even check his hotbars because they are off the screenshot. Also you would also think someone with that high of a hit would have higher dps/overall damage.
Also the dropbox linked images don't work.
My guess would be the jugg/guardian bug combined with a well timed smash. Wasn't a setup, but not a real number. Like when I got my 5k medal by throwing a thermal grenade.