Before ragdoll physics were introduced to the Halo franchise, pre-made death animations stood in their place. The thing is that some of these pre-made animations made their way into later Halo titles, and even in Halo 3 you’d sometimes see a death animation taken straight from Halo: Combat Evolved (I.E. the breakdance of death.) Most of the Halo games have ran on the Blam! engine, but is there any particular reason why these animations would carry over from game to game?
I couldn’t find a GIF of this happening, but here’s the aftermath of the animation.