A student gunman on Friday shot one student at Arapahoe High School before being killed by a self-inflicted gunshot wound, law enforcement officials reported.
Law enforcement officials late on Friday night identified the student gunman as 18-year-old Karl Halverson Pierson.
One student was taken to surgery at a local hospital for what officials describe as serious injuries sustained during the attack while a second student was treated for minor wounds.
Arapahoe County Sheriff Grayson Robinson told reporters during a media briefing on Friday that the shooter was a student at Arapahoe High School and was found deceased in a classroom by law enforcement on the scene.
Robinson provided new information late Friday night that the primary victim, described as a 15-year-old female, underwent surgery and remains in critical condition.
The second female was first believed to have suffered an injury from a gunshot but Robinson clarified the report on Friday night to say that no injury was sustained.
Sheriff Robinson said on Friday evening that the identity of the victim would be released at a later time.
"The alleged shooter entered the school carrying a shotgun," Robinson said. "He made no effort to hide it or conceal it."
Upon entering the school, the shooter asked nearby students where he could find a particular teacher.
Law enforcement officials say the shooter did not encounter the teacher who left the building after learning of the shooter’s inquiry.
Authorities also have not released the identity of the teacher.
Robinson also said that police entered the building with adequate weapons but did not discharge any weapons inside the school.
The number of shots fired by the shooter remains unknown at this time.
Robinson maintains that there's reason to believe that the shooter acted alone but assured the public that a thorough investigation will be conducted.
“It continues to appear to us that the shooter who is deceased was the lone actor in this tragic event but we will continue to try to confirm that,” Robinson said.
There is no current indication, according to the sheriff, that the incident is connected to the anniversary of the Sandy Hook Elementary shootings, which occurred a year ago this Saturday, December 14.
Arapahoe High School will remain closed through the weekend and Monday classes are canceled.
Officials said that additional information and instructions regarding classes for next will be provided at a later time.
Megan Verlee, Mark Bevis and Elaine Grant contributed to this report.