Basically I was walking towards a teammate who was aiming a ranged weapon into the distance. Suddenly a marauder spawns out of nowhere a few steps behind them, turns and attacks them once and they go down. I didn’t get a picture because it happened so fast.
Until now I’ve only seen this bug in glitch montage videos but I finally saw it with my own eyes. It’s an extremely rare bug but evidently it’s still around in 2.0.15