Supposedly he made a rope from his bedsheet and attached it to the bed, got on his knees and asphyxiated himself. Takes 7lbs of pressure on the neck arteries to pass out, once passed out the bodyweight keeps the blood flow cut off. It is not like hanging from a standard gallows design which is to break the neck, not asphyxiate.
He may have done some twisting to tighten the rope...he’s a sex offender he’s probably seen plenty of sex related ‘asphyxiation’ and has a good idea of how close you can go and not come back.