Complex sentence: Mulder returns to Berube's house and finds Secare in the attic, but he is killed by the Crew Cut Man and due to exposure to Secare's blood, Mulder passes out and is captured.
Split into simpler sentences: Mulder returns to Berube's house and finds Secare in the attic, but Secare is killed by the Crew Cut Man. Due to exposure to Secare's blood, Mulder passes out and is captured.