From Halopedia, the Halo wiki
During the Covenant's attack on Mombasa, Uberti hitched a ride in the Olifant that Sadie Endesha and Mike Branley were using to travel through the Covenant -occupied New Mombasa and tried to sell them siding materials. When he overheard that some of the Covenant species were friendly, he overreacted; opened the Olifant's top hatch and tried to "negotiate" with a nearby Zurdo-pattern Wraith, saying that it was a down market, being a salesman. Sadie and Mike immediately exited through the Olifant's back ramp, narrowly avoiding death. Uberti wasn't so lucky; the Wraith obliterated the vehicle, and he was killed instantly.