A Forestville teenager pleaded guilty Tuesday to fatally stabbing a 92-year-old neighbor who had acted like a grandmother to him and then making off with her credit card and cash last summer, authorities said. William Fitts, 16, pleaded guilty to second-degree murder, first-degree burglary and theft in the killing in August of Thelma Steele, authorities said. Prosecutors said that Fitts stabbed Steele several times with a pocketknife after the two argued about family issues and that he then left her for dead on the couch in her home. Her body was not discovered for several days, after Fitts’s family became...