Manuel Mendoza

Private Manuel Mendoza was one of the Marines who survived the crash landing on Installation 04. He was part of Fireteam Charlie, who were led by Captain Keyes to find the "weapon cache" that they thought the Forerunner had left on the Halo. Instead, it turned out to be the main holding area for the Flood, and all of their team, save for Sergeant Johnson were taken by the Flood, and turned into Combat Forms. Mendoza attempted to escape the room, but the Flood were able to infest him before he did. The Master Chief noted in his debriefing that he had an encounter with Mendoza as a Flood form while on the Halo, and was forced to kill him in self-defense.

Trivia
There is also a glitch in Halo: Combat Evolved that allows you to get back on board the Pelican in the level 343 Guilty Spark. Once the Pelican lands, the player may run around the perimeter of the level, where Private Mendoza stands. Also by doing this, the player can skip most of the outdoor portion of the level. To do this throw a grenade as the pelican is landing and you will stay inside the ship. It will then crash some way away and you can explore the upper area of the level.