MEXICO CITY — A gunman opened fire Monday from a pyramid in the famed Mexican archaeological site of Teotihuacán, killing a female Canadian tourist and wounding six others. At least seven other people were injured as tourists scrambled to escape the gunfire. The shooter later took his own life, officials said. The injured included six U.S. citizens, one of them a 61-year-old woman, as well as a 6-year-old boy from Colombia and two other Colombian nationals. Two Brazilians, one Russian and one Canadian were also injured. At least six of the injured suffered gunshot wounds, authorities said, while others apparently were hurt in falls while trying to escape. There was no immediate breakdown on the conditions of the injured, all of whom were being treated in area hospitals, authorities said. Various Mexican media outlets, citing police sources, identified the assailant as a 27-year-old Mexico City resident who had expressed admiration for Hitler and for the perpetrators of the 1999 Columbine High School massacre in Colorado. Monday’s attack occurred on April 20, Hitler’s birthday, and also the anniversary …