From Halopedia, the Halo wiki
During an unspecified battle, Hauser and his Marines were pinned down by massing Covenant forces after he gave the order to retreat from their previous location. Chief Petty Officer Daisy-023 soon arrived and assisted them in eliminating all Covenant infantry in the immediate vicinity. Once the Covenant forces were eliminated, Gamma Team was able to establish radio contact with Ralph-103.
The group then traversed to a Covenant-occupied landing zone to be evacuated by a D77-TC Pelican. Sergeant Hauser scouted the area and found an M12 Chaingun Warthog, and the group attempted to use it to reach the landing zone as soon as possible. Daisy-023 manned the vehicle's turret as Hauser drove toward their destination. However, a Sangheili soldier managed to overturn the vehicle with a plasma grenade.
Daisy-023 managed to pull a wounded Hauser out of the wreckage and toward the Pelican. During the process, however, a needler-wielding Sangheili pushed Hauser out of the way and fatally wounded the Spartan. Hauser made it to the Pelican, but Ralph refused to leave without her. The two unsuccessfully attempted to save the Spartan's life, leading to the destruction of the Pelican and the deaths of all those aboard.
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