Complex sentence: Initially only known as "Hispanic Man", he was a Nicaraguan mercenary working for Cigarette Smoking Man, briefly partnered with Alex Krycek, at which time he killed Scully's sister, Melissa, in a case of mistaken identity.
Split into simpler sentences: Initially only known as "Hispanic Man", he was a Nicaraguan mercenary working for Cigarette Smoking Man. Whilst briefly partnered with Alex Krycek, he killed Scully's sister, Melissa, in a case of mistaken identity.