MUNICH — The gunman whose rampage at a Munich mall left nine people dead was a depression-plagued teenager who avidly read books and articles about mass killings and apparently tried to lure young victims to their deaths through a faked Facebook posting, authorities said Saturday. Information from witnesses indicated that his hatred of foreigners might have played a role in the mass shooting, even though he himself was the German-born son of Iranian asylum-seekers. Most of the dead were youths and all were Munich residents of varied ethnic backgrounds.