Getty Images - Sheriff Grayson Robinson

The sheriff of Arapahoe County in Colorado says there's no question the student who went on a shooting spree at Arapahoe High School earlier this month was a murderer. Sheriff Grayson Robinson remarked today that the shooter entered the high school with the intention to do the maximum amount of damage. During a press conference, Robinson repeatedly called the gunman "the murderer." He added that the entire incident, from the time the shooter entered the high school to the moment he was dead of a self-inflicted gunshot wound, took less than one and a half minutes.

Robinson said the investigation into the attack continues, but so far there's no evidence that anyone else was involved in planning and carrying out the shooting. He remarked that the shotgun used in the attack was bought about a week before the December 13th shooting. Student Claire Davis was shot in the head, and died on December 21st, and a memorial will be held for her on Wednesday. (Metro Networks Inc.)