CNN  —  Tall and disheveled, with a scraggly salt-and-pepper beard, Ramon Rivera was just one month out of jail when he approached a construction worker early Monday and fatally stabbed him without saying a word, police said. He was not done, police said. An urban nightmare was unfolding on a mild autumn morning in New York. The 51-year-old made his way across Manhattan and, more than two hours later, police and prosecutors said, he fatally stabbed a fisherman and then a woman sitting on a park