and a study about sleep aids says they hardly improve the sleep of workers following the night shift. they say users' alertness was only slightly improved when they were awake. those are some of the top stories on this wednesday, august 13th. >> announcer: from abc news, this is "world news now." good morning to you. great to have you with us. we begin this half hour with new details surrounding the death of robin williams. >> fans, friends and family are still stunned this morning as we find out more about how the hollywood legend ended his own life. abc's cecelia vega is in san francisco. >> reporter: new details about robin williams' final hours. at 10:30 p.m. sunday night, williams was last seen alive by his wife, susan schneider. investigators say she woke up monday morning and left their house thinking her husband was still asleep. but just before noon, his personal assistant discovered his body. distraught she called 911. emergency crews responded in minutes. >> apparent suicide attempt by hanging.