I started speedrunning to round 5 on Black Ops DS Zombies, and came across this. The zombie entered through a window and almost immediately after touching the ground, it randomly died.

Its death did seem to align with me pressing the button to throw the knife, but not only was the animation not played, but my crosshair wasn't over its head. Is this a known glitch? If so, would it be possible to utilize the glitch for faster runs?