The world's oldest known person has died in Los Angeles at age 115. Gertrude Baines died today at a hospital, probably of a heart attack; an autopsy will determine the exact cause. Baines was born in 1894 in Shellman, Ga., and she got a letter from President Obama on her last birthday, in April. The oldest person in the world is now 114-year-old Kama Chinen, who lives in Japan. (More Gertrude Baines stories.)