Police say a Philadelphia college professor killed himself by diving over a second-floor railing inside a campus building during class, the Huffington Post reports. The newspaper says the 71-year-old professor walked out of his class Wednesday, returned briefly, yelled and then ran to a second-floor railing outside the classroom. Police say campus security was summoned and Alexandrov dived over the railing and hit the floor, some 20 to 30 feet below…