A Houston teenager is accused of shooting dead a fellow teen as part of a weapons-drawing prank that has been spreading on social media, authorities said Thursday. Mohamad Nour Alajil, 18, has been charged with manslaughter in connection to the Dec. 11 slaying of Christian Johnson, 19, officials said. Police believe Johnson's death resulted from the "No Lackin'" challenge, which calls for one person to pull a weapon on another on video to record the reaction, KPRC reported. The challenge stems from the notion that no one should ever be caught without, or "lacking," a gun. Johnson had an AR-15...