Kappus

Private Kappus was a tech specialist in the squad that also housed Private Manuel Mendoza, Private Bisenti, Private Riley, Private Jenkins, and Sergeant Johnson.

He was a Tech Specialist in Covenant and Forerunner technology. One of his tasks was opening locked doors. He was ordered by Captain Keyes to open the door that just so happened to be the only thing holding back the flood. Unwillingly and unknowingly, Kappus unleashed the Flood on Installation 04, dooming him and the rest of his squad, save for Johnson. When an Infection Form attached itself to Kappus's friend, Riley, he got it off successfully. Kappus was soon transformed into a Combat Form, though. The Master Chief had discovered in his debriefings that he had an encounter with Kappus as a flood combat form while on Halo and had to kill him in self-defense.

Trivia
His role in the game is often mistaken for that of Mendoza's.