Agent Mallory is an SCU agent that appears as the protagonist of the official online game, Condemned: The Prequel Story. His assignment is to investigate a recent series of murders, where the killer would place a photograph of the victim somewhere near their body. Mallory travels to various locations in search of evidence, but ultimately finds the killer himself dead by his own methods, making him the first victim of Serial Killer X in the playable canon.
Agent Mallory is soon attacked by SKX, presumably out of necessity as Mallory had solved the case roughly as fast as SKX could have, causing him to arrive within minutes of SKX's farewell to the "Polaroid Killer." Mallory fights back against SKX and enters a deadly game of cat and mouse, but ultimately the older man is surprised and beaten to the ground by SKX, who promptly delivers a killing blow.
Neither the Polaroid Killer nor Agent Mallory are mentioned in Condemned: Criminal Origins. Because Mallory never spoke to anyone about his findings, it is likely assumed by SCU that he was killed by the Polaroid Killer, whose case then went cold.