Centennial: Police on Saturday sought to learn why a teenager stormed through his suburban Denver school with a shotgun and Molotov cocktails, opening fire on a fellow student before taking his own life in the latest burst of US school gun violence.
Arapahoe County Sheriff Grayson Robinson said detectives were investigating revenge as a possible motive for Friday`s shooting.
But he has declined to elaborate or to comment on unconfirmed reports that the suspect, identified as Karl Pierson, may have been angry at having been demoted from or kicked off the school debate team.
Police said the student gunman`s intended target appeared to be a teacher who Pierson was calling out for by name as the armed teenager stalked through the hallways of Arapahoe High School.
The faculty member, who police have not publicly named but who local media accounts, citing eyewitnesses, have identified as school librarian Tracy Murphy, fled the building unharmed.
When the suspect started shooting, a 15-year-old girl, who authorities say was in Pierson`s line of fire though apparently not an intended victim, was severely wounded.
A second girl who was initially thought to have been wounded was not injured, but spattered with blood from the teenager who was hit as staff and students scurried for cover.
Sheriff`s deputies and police converging on the school encountered heavy smoke in the building from a Molotov cocktail-like incendiary device Pierson had set off, one of two he was carrying.
Pierson, who had entered the school brandishing a shotgun, was found by police about 15 minutes later in a classroom, dead from a self-inflicted gunshot wound, the sheriff said.
Robinson said the teen appeared to have killed himself as law enforcement officers closed in, though officers never fired a shot.