From Halopedia, the Halo wiki
Murray was a prison guard aboard the prisoner transport Mona Lisa. He was not regarded highly by Patrick Rimmer, who referred to him as a "fat asshole". After ONI Major John Smith had come aboard the ship, Murray discovered that the Naval Intelligence personnel were using the prisoners—both Covenant and human—to experiment on the parasitic lifeform known as the Flood. He would then inform some of the prisoners of this, including Rimmer.
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