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Battle of Earth
During the start of the Covenant invasion of Earth, Perez and the rest of A Company were sent to reinforce the defenses of New Mombasa, Kenya, which was under attack by Covenant forces from the CAS-class assault carrier Solemn Penance. The Master Chief met the Corporal in the proximity of a Marine field command post in a Mtangulizi Kampuni building where some Marines were held up, wounded, and making a last-ditch stand against the Covenant. He led the Master Chief to Staff Sergeant Banks' position on the roof.
Search for the Index
Perez was mentioned, but not seen, during the Battle of Installation 05, in which the UNSC forces and the Arbiter raced against each other to gain possession of the Activation Index, while the Flood tried to stop them. McKenzie and Perez were with Miranda Keyes and Sergeant Avery Johnson, and evidently the only two Marines to reach the Index chamber alive.
McKenzie and Perez were tasked with securing the exit from the chamber, but it is unknown what exactly happened to them during this endeavor. They may have been killed by the Flood, killed by the Arbiter, or captured/killed by the Brutes, as when Johnson calls them for their status, they do not respond. The Arbiter arrived shortly after, capturing Keyes, Johnson, and the Index.
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