The student who opened fire at Arapahoe High School in Centennial, Colo., last week, died of a single gunshot wound to the head, the county coroner said on Monday.
"Karl Pierson, 18, committed suicide after critically wounding a student in the Arapahoe High School on Friday. Pierson had entered the school looking for the librarian and debating coach with whom he had a dispute, officials said.
"According to a statement by the coroner's office, Pierson's death was from 'a severe head injury due to a shotgun wound to the head. The manner of death is classified as suicide.'"
The Denver Post reports that the school has cancelled classes for the rest of the year and the 17-year-old victim is in critical condition.
The paper adds that a motive is still elusive:
"Pierson bought the shotgun days before, part of a plot to avenge a grudge he had against the school's librarian and debate coach, Tracy Murphy. Arapahoe County Sheriff Grayson Robinson told The Post on Sunday that investigators have spoken with Murphy extensively and are working to understand the relationship between the two.
"'We're beginning to better define that, but at this point in time it's not something we're going to talk about,' Robinson said."