Former Aurora PD sergeant charged as accessory in pipe bombings Curtiss Christensen is accused of buying weapons for the suspect and then donating a vehicle he knew was used in the crime, an affidavit says. Author: Janet Oravetz (9News) Updated: 4:52 PM MST March 11, 2021 AURORA, Colo. — A former Aurora Police Department (APD) sergeant who retired in 2006 has been arrested and charged as an accessory related to two pipe bomb explosions in December and January. Court documents show that Curtiss Christensen has been charged with the following: Firearms - straw purchase Tampering with physical evidence He was arrested as part of the investigation into pipe bomb explosions in Aurora on Dec. 25, 2020, and Jan. 7, 2021, according to an arrest affidavit.