A student carried a shotgun into his Colorado high school on Friday, asked for a teacher by name and then shot two students before killing himself, law enforcement officers said.  One student, a teenage girl, was transported in serious condition to hospital, from the scene at Arapahoe High School, south of Denver. A second student suffered a minor gunshot wound and was expected to be released from hospital later on Friday.  “The shooter is dead as a result of a self-inflicted gunshot wound, so there are no immediate threats at this time,” Arahapoe county sheriff Grayson Robinson said, outside the school. “Unfortunately we have one student who was injured.”  The shooter was later named by authorities as Karl Halverson Pierson.  In a news conference on Friday afternoon, Colorado governor John Hickenlooper condemned "this all-too-familiar sequence, where you have gunshots, and parents racing to the school and this unspeakable horror in a place of learning".  The high school is about 15 minutes from Columbine High School, the site of a 1999 shooting in which two gunmen killed 12 pupils, a teacher and themselves. The incident took place a day before the one-year anniversary of a shooting incident at Sandy Hook elementary school in Newtown, Connecticut, in which 20 children, six staff, the shooter and his mother died.  Police described a chilling sequence of events at Arapahoe after the shooter, who police said they had identified but whose name they did not release, entered the school by a West entrance.  "The student that was armed with a shotgun as he entered the west side of Arapahoe, immediately asked for the location of this specific teacher, and asked for that teacher by name," Robinson said. "The student that entered the high school was armed with a shotgun. He made no effort to hide it or conceal it.  "Word got around immediately that he was looking for the teacher."  When he heard he was the target, the teacher left the school, the sheriff said. "He took himself away from the school, with an effort to try to take the shooter with him," Robinson said.  The student in serious condition was probably not targeted by the shooter, the sheriff said. "The student was simply in the area with the shooter, and was shot at the time the shooter came through the school," he said.  Police entered the school shortly after initial reports of shots fired were made at 12.33pm local time. Dozens of law enforcement vehicles converged outside the school shortly after the first reports.  Robinson said officers had found the shooter’s body in a classroom “quite a ways into the school”, within 20 minutes of the report of the shooting.  Arapahoe High School is part of the Littleton school district, in the Denver suburb of Centennial. It has approximately 2,100 students.  "Those [active shooter] protocols, unfortunately, have had to be used far, far, far too many times in the state of Colorado, and across the United States,” Robinson said.
• At least one student injured after gunman opened fire at school• Governor condemns 'all-too familiar, unspeakable horror'