UPDATED 10:00 p.m. ET: Authorities have identified the shooter as 18-year-old Karl Halverson Pierson.

The victim reported to be in critical condition is a 15-year-old girl and it's unclear if Pierson intentionally shot her. Arapahoe County Sheriff Grayson Robinson also "did not elaborate on any possible motive."

UPDATED 5:15 p.m. ET: Authorities will not release the name of the suspected shooter, although the sheriff did confirm that person was a student at the school.

The "gunman asked for the location of a specific teacher, who heard he was being looked for, and left the school 'in an effort to draw the student away from the school.'"

A second student was injured during the incident, although that person was not shot.

One student at the school said he became aware of the incident after hearing "three bangs."

UPDATED 4:20 p.m. ET: According to an Associated Press report, the suspected gunman killed himself.

UPDATED 4:00 p.m. ET: The Denver Post is reporting the suspected shooter is dead.

UPDATED 3:50 p.m. ET: The Associated Press is reporting one student is in critical condition.

Police in Centennial, Colorado say there's an "active shooting situation" at Arapahoe High School.

There are potentially two victims, although their condition is unclear.

 

Arapahoe High School is in a nearby district to Columbine High School, which was the site of an infamous 1999 mass shooting spree.

It's also worth noting that tomorrow will be the one-year anniversary of the tragedy at Sandy Hook Elementary School in Newtown, Connecticut.