From Halopedia, the Halo wiki
During the Battle of Mombasa, he was guarding the NMPD headquarters when former policeman Marshall Glick arrived and went on a killing spree against his former co-workers, whom he believed had "wronged" him in one insignificant way or another.
Jim was unaware of Glick's homicides until he entered the lobby of the building while discussing the unclear reasoning for shutting down the Superintendent on his chatter. Upon seeing his dead friends, Jim initially believed that the Covenant had killed them, but Glick soon appeared and corrected him. Marshall's justification for killing Jim was that Jim regularly used his half-and-half, even though it was labelled.
Later on, Jim, along with Roberto Bustamante (another policeman that Glick killed) and Glick, were touted as heroes by the Propagandist Stephen, who said they were all killed by Covenant snipers (who were in turn killed by the civilian resistance, who had made a makeshift flamethrower out of a can of gasoline and a leaf blower).
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