A 31-year-old woman was arrested Wednesday for allegedly killing her two-year-old son by wrapping a Japanese-style "futon" mattress around him at their home in Tokyo, police said.The mother, Haruka Takeda, has told investigators she wrapped Sotaro with the futon because he would not stop crying, but denied she meant to kill him. She said she had done so in the past when he would not stop crying.The police suspect Sotaro died of suffocation, between 8:50 p.m. and 9:40 p.m. Tuesday.Related coverage:Suspect in Japanese woman's murder faces July extradition to FranceREAD FULL ARTICLE