Former Zappos CEO Tony Hsieh developed a fixation with fire and tried to deprive himself of oxygen in the months leading up to his November death from a house fire, the Wall Street Journal reported on Sunday.

According to the WSJ, Hsieh struggled with drug abuse, isolating himself away from friends in family and moving to the resort town of Park City, Utah. A friend who visited Hsieh at his Utah mansion told the Journal he saw a thousand candles there, which Hsieh told him were “a symbol of what life was like in a simpler time.” On the night of the fatal fire, Hsieh went to a shed attached to his girlfriend’s home in New London, Connecticut, with the purpose of using a heater to lower the oxygen level, according to the Journal, telling people to check on him every five minutes. The cause of the fire has not yet been determined. Hsieh, 46, died nine days later, with a medical examiner ruling his death an accident.