Hanged himself in his cell. That sucks for the women if they don't feel closure now.
http://www.cnn.com/2013/09/04/justice/ariel-castro-cleveland-kidnapper-death/index.html?hpt=hp_t1
http://www.cnn.com/2013/09/04/justice/ariel-castro-cleveland-kidnapper-death/index.html?hpt=hp_t1