Halo: Legends Season 1 Episode 2

Origins Part 2

The Forerunners realize the futility of their actions. They build the Halo network at the Ark and then dispersal them throughout the universe. After the cataloging of all sentient species (of which an early Elite, Brute, Jackal, Grunt, and Human society are shown) The Forerunners activate the Halo rings and wipe out all traces of themselves and the Flood.