Weird Figure in the Weld Shop

…My one coworker had already went home early and the other was in the machining shop talking to another coworker. I was alone. ALL shop fans were off, ALL welding machines were off so it was library quiet. ALL 3 doors to the weld shop were closed tight. It’s very bright in the weld shop due to the floured lights Yet something/someone dark dark green ducked down very QUICKLY behind a portable green Welding Curtain….