Today in history: On April 20, 1999, two students shot and killed 12 classmates and one teacher and injured 23 others before taking their own lives at Columbine High School, near Denver, Colorado. Also on this date: In 1812, the fourth vice president of the United States, George Clinton, died in Washington at age 72, becoming the first vice president to die while in office. In 1912, Boston’s Fenway Park, now the oldest active stadium in Major League Baseball, hosted its first official baseball