Police & fire crews responding to shooting at Arapahoe HS in Centennial, Colo., on Fri., Dec. 13, 2013. (KUSA)
CENTENNIAL, Colo. (WXIA) -- Police said a student is dead from an apparent self-inflicted gunshot wound after a shooting at a Centennial, Colo., high school that left another student in critical condition.
Arapahoe County Sheriff's Department officials said the shooting suspect, Karl Halverson Pierson, a male student at Arapahoe High School, entered the school during the lunch timeframe, and was looking for a particular teacher.
Officials said that when the teacher learned that Pierson was there looking for him, and that he was armed, he left the school -- which officials said was the proper course of action.
PHOTOS | Colorado high school shooting
A 15-or-16 year-old female student who confronted the suspect was shot. That student was taken to Littleton Hospital, where she was listed in critical condition.
The 15-year-old female shooting victim is in critical condition. There was some initial confusion about a possible second shooting victim, but Arapahoe County Sheriff Grayson Robinson said later in the evening that the second victim had only appeared to have been shot.
The second victim who was initially thought to have been shot was transported to Swedish Medical Center in Englewood. There it was determined she was not shot. The blood found on her was from the first victim.
A third victim suffered an anxiety attack and was transported to a local hospital for treatment.
Two other students suffered emotional attacks but were treated at the scene, according to investigators.
Law enforcement officials said they conducted a search following the shooting, and discovered Pierson dead in a classroom, from what appeared to be a self-inflicted gunshot wound.
Authorities said the suspect made no effort to conceal the weapon he was carrying as he entered the school. They said he was able to get "very deep" within the school.
Officials said two devices, described as Molotov cocktails, were found inside the school building. One device was detonated by the suspect, while the other was located and rendered safe by authorities.
Officers who arrived at the school said they had to contend with smoke from the detonation of the first device -- which officers said was a bottle-based improvised incendiary weapon.
As students were being evacuated from the school, shortly after the incident occurred, they were being patted down by police.
"The kids have been through a traumatic situation," Arapahoe County Sheriff Grayson Robinson said. "We need to ensure that anyone we evacuate isn't part of our problem. We're doing the evacuation slowly and deliberately."
Officials said Arapahoe High School would be closed on Monday.
Arapahoe High School is in Arapahoe County, northeast of Denver. According to KUSA, there are 70 classrooms on the 254,000 square-foot high school campus. The school has a student population of 2,229 and the present school was constructed in 1964.
(KUSA Denver and NBC News contributed to this report.)