CENTENNIAL, Colo. - A 17-year-old senior who was shot inside Arapahoe High School Friday remains in critical condition.

The gunman -- whom CALL7 Investigators first identified as senior Karl Halverson Pierson -- died from an apparent self-inflicted gunshot wound and was found in a classroom by a deputy who had called for additional help to the "active shooter" situation just 5 minutes earlier.

The student gunman who shot her was targeting the school faculty member who had just kicked him off the school's debate team, the CALL7 Investigators have learned.

The faculty member, identified by sources school librarian Tracy Murphy, escaped without injury.

"This shooting was the result of revenge on the part of the shooter because of a confrontation or a disagreement between the shooter and the teacher that the shooter was looking for when he entered the school just before 12:33," Arapahoe County Sheriff Grayson Robinson said. "However, there was no warning, no threat beforehand."

Detectives are executing a search warrant at the gunman's Highlands Ranch home, Robinson said.

Officers are also searching the car he left in the school's west parking lot and his father's home in Denver, Robinson said.

Robinson also clarified on Friday night that there were not two gunshot victims as reported earlier. There was just one victim, who is in critical condition at Littleton Hospital, where she underwent surgery earlier Friday.

The other student initially believed to have been shot was just covered in blood from the first victim.  The second victim was taken to Swedish Hospital as a precaution and released.

Three students suffered anxiety attacks during the school evacuation, Grayson said. Two of those students were released to their parents and the third student was taken to Swedish where the student was treated and released.

Two Molotov cocktails were found inside the school, Robinson said. One was detonated inside the school and may have caused the significant amount of smoke deputies were faced with when they first responded to the scene.

The second device was found inside the school during the search after the shooting. It was rendered safe and was never deployed, Robinson said.

-- Janitor: Student wearing tactical gear ran through school --

The shooter was armed with a shotgun and was looking for a specific teacher that he identified by name when he ran into the school, Robinson said.

The shooter walked into the west side of the school at 12:33 p.m. on Friday.

Custodian Fabian Llerenas told 7NEWS that he saw a student dressed in military or tactical gear running through the school. He thought the black object swinging on the gunman's arm was a guitar case.

"It just looked weird," Llerenas said. "He went in and that's when I heard two pops. That's when I knew. I said, 'They are shooting in the school.'"

Llerenas said he called for help and took the threatened staff member with him to his truck.

"He knew he was the target," Robinson said as he praised the teacher for leaving in hopes that it would help remove the threat from the school.

"When the teacher found out, he exited," Robinson said.

Seconds later, Robinson said, a student was shot.

Initially, Robinson said that student had confronted the gunman, but later Robinson said that student may have simply been in the area and was shot.

Arapahoe High School student Courtney Leytoldt told 7NEWS she heard a girl running down the stairs yelling, "Help me, help me, there's a shooter." She said that girl was covered in blood.

Leytoldt said she was in yoga class and that her teacher put all the students in a closet to protect them.

-- 'Active shooter' protocol worked --

Robinson said as soon as the first deputy was notified of the situation, he followed the "active shooter protocol" to call for help and then immediately seek out the threat and search for the gunman.

"The officer went immediately to the threat, as he was trained," Robinson explained. "Try to go to the threat and eliminate the threat."

"Within 5 minutes, [deputies] found the suspect dead inside the school," Robinson said. "Appears to us that the shooter is dead as the result of a self-inflicted gunshot wound, but that is under investigation."

Thousand of students were evacuated safely but had to hold their hands in the air and be searched before they left the school grounds.

"They were evacuated very slowly, deliberately and meticulously," Robinson explained.

He said deputies wanted to make sure there were no other students or individuals that were collaborating with the suspect.

Robinson said that the gunman acted alone.

-- Parents reunite with kids, districts react to lockdown --

Hearing of the lockdown and shooting by students inside the school, panicked parents fled to the high school and were told to go to Shepherd of the Hills Church and Euclid Middle School, where they would be reunited with their children after they are cleared by officers.

Robinson said there is no indication that there is a tie between the shooting at Arapahoe High School and the one year anniversary of the deadly school shooting at Sandy Hook Elementary School on Saturday.

Arapahoe High School is at 2201 East Dry Creek Road in Centennial. It is part of Littleton Public Schools, which locked down all schools Friday afternoon when there were initial reports of a shooting.

Several other school districts went on alert, declaring lockdown or secured perimeter including Elizabeth schools, Cherry Creek Schools, Douglas County Schools and Aurora Public Schools.

More than 2,100 students attend Arapahoe High School where nine out of 10 graduates go on to college, according to the Littleton Public Schools website.

-- No school at Arapahoe High School on Monday --

Robinson said investigators will be at the school,  investigating the case all weekend. Students and staff who left behind personal belongings probably won't have access to it until Monday afternoon.

"We will do this investigation right. We will not do it quick, and that is by design," Robinson said.

Among the evidence investigators will be looking at are surveillance cameras found throughout the school. They will also be interviewing and re-interviewing the 65 to 80 students who were in the immediate area of shooting.

However, cars that were left in the school's parking lot could be released to their owners at 8 a.m. Saturday.

There will be no school at Arapahoe High School on Monday, the Littleton Public Schools Superintendent Scott Murphy said. Murphy said he will decide on Monday when the school will reopen.

Counseling will be available to students, parents and anyone in the community on Saturday at two locations from 9 a.m. to 2 p.m.:

-- Powell Middle School at 8000 S. Corona Way

-- Shepherd of the Hills Lutheran Church at 7691 S. University Blvd.

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