A transgender teenager has pleaded guilty to murder after opening fire on fellow students who he says bullied him. Alec McKinney faces a life sentence over the shooting rampage at the Science, Technology, Engineering and Math (STEM) School near Denver, Colorado, that left one student dead and injured eight more on May 7. McKinney's friend Devon Erickson, 19, is also accused of carrying out the attack, and pleaded not guilty last month to the same charges of murder and attempted murder. Kendrick Castillo, an 18-year-old pupil at the school in Highlands Ranch, was fatally shot when he charged one of...