Sean McCallum (ショーン・マッカラム, Shōn Makkaramu) is introduced in Xenosaga: Pied Piper as the Chief of the 1875th Federation Police Special Ops Command. Jan Sauer is his subordinate and reports directly to him. McCallum is described as stubborn yet kind to his subordinates. He is loyal to a fault, committed to following orders even when he feels that they are unjust.
Jan Sauer (foreground) and Sean McCallum discussing the Voyager investigation in McCallum's office.
Previously, McCallum worked for Jan's father, who was also a Federation police officer and was killed in the line of duty. It is implied that McCallum had a close personal friendship with Jan's family, and that he continued to support them after the death of Jan's father. As a result, Jan views him as an adoptive father figure. In a flashback to Jan's childhood, Jan refers to McCallum as "Uncle Sean" (ショーンおじさん / Shōn ojisan).[1]
During Pied Piper, McCallum supervises Jan and his team as they investigate a series of murders committed by the U.M.N. terrorist Voyager. When Dmitri Yuriev attempts to shut down the investigation to conceal his own involvement in the killings, he appoints Ernest Luis in McCallum's place. McCallum is then arrested along with Jan and several of his colleagues. When Jan and the others escape from prison, they find McCallum fatally injured in his cell. He dies in Jan's arms after praising Jan for becoming "a true legacy of your parents" and urging Jan to protect his subordinates.