Pictured: The high-achieving senior who shot female student, 15, and killed himself after taking Molotov cocktails and shotgun to school 'to take revenge on debate coach who demoted him'

Three students injured and the gunman found dead at Arapahoe High School in Centennial on Friday afternoon

Gunman Karl Pierson entered school and said he was targeting librarian Tracy Murphy who also worked as the speech and debate team coach



Pierson is thought to have been demoted within the ranks of the speech and debate team earlier this week and may have been suspended



He showed friends pictures of the shotgun he used for hunting

Two explosives were found at the school- one was smoking and the other was disarmed by responding officers



Pierson, a senior at the school, has been described as 'geeky' and 'sweet'



Arapahoe is just miles from Columbine High School - where 13 were killed in 1999 - and the Aurora movie theater where 12 were shot dead last year

It also comes on the eve of 1-year anniversary of the Sandy Hook shooting



The shooter: Karl Pierson, a senior at Arapahoe High School, has been named as the shooter who killed himself and injured three others

The high school senior student who walked into his Colorado high school with a shotgun and two explosives was targeting the librarian and was upset over the fact that he had been benched from the debate team earlier this week.



Karl Pierson has been identified as the shooter who went into Arapahoe High School at around 12.30pm Friday afternoon asking for the librarian by name. Reports say that he did not conceal his shotgun and word traveled to librarian Tracy Murphy- who doubled as the speech and debate team advisor- that he was the target.



Police responded to the scene and found Pierson, 18, had injured three other students and shot at the librarian but missed, before killing himself with a self-inflicted gunshot wound.



A fellow student told local news station KDVR that he was coming back to school after running an errand during his lunch break and was in the parking lot when he saw the librarian running out of the building.



‘He seemed incredibly shocked, he was in awe,’ student Frank Warnoff said of Mr Murphy.



Warnoff said that Murphy kept telling him what happened inside, naming Pierson and saying what appears to be the motive for the shooting.



‘I docked him from the speech and debate team and that just shocked him,’ Warnoff recalled Murphy telling him.



‘(Mr Murphy) just kept repeating (the shooter’s) name and what happened and where (the shooter) was.



Debate team: Karl Pierson (left) was a member of the debate team and previously competed at nationals for the school, but his coach, librarian Tracy Murphy (right) allegedly demoted him earlier this week causing him to snap

Sheriff Grayson Robinson said at an afternoon press conference that the shooter was a current student at the school but other reports suggested that he may have recently been suspended.



The police have not publicly released Pierson's name, but public records and local news reports, as well as debate team and cross country team listings all point to Pierson as the shooter.



‘I could see a bit nerdy and geeky but in a sort of charming way,’ Warnoff said.

‘I could see that he was bullied but he was always very humble and down to earth, always in a good mood and energetic. I just never saw him as this kind of person.’



Aside from the self-inflicted gunshot wound, the other injuries were sustained by three students, two of whom were injured by the shotgun and the third who sustained some other kind of unspecified injury.

Hands up: Police search students as they are led out of the school with their hands in the air on Friday afternoon. Two students were injured after a gunman opened fire before he shot himself



Fears: Students comfort each other at Arapahoe High School following the shooting Under investigation: A full team of police are swarming this house in Highlands Ranch (pictured before the investigation) as it is thought to be where the shooter lived Warranted: Police prepare to search the Pierson home for explosives after finding two at the high school One of the injured students has been released from the hospital, another remains in the hospital but is in good condition and the third is still in serious condition at Littleton Hospital.

The student in serious condition is believed to be a female student. Some reports say that she happened to be in the same area as the shooter when he shot at her but others say she tried to intervene and stop him.

Mr Murphy told Warnoff that ‘he was shot at but he missed he was able to dodge the blast of the shotgun’. RELATED ARTICLES Previous

1

Next Hollywood publicist was shot in the heart in fatal attack as... Share this article Share Local station KDVR reports that Pierson was suspended earlier this week after shouting at a teacher. Others in the school were apparently aware that the student was having a difficult week because the otherwise calm and happy student seemed to snap.

‘I wasn’t there but I heard in one of his classes on Wednesday he went out to get something from his locker I believe, came back and started pounding on the door because it was locked. They just couldn't figure out how he was so upset,’ Warnoff said. Heartbreaking: Student Dominika Kostecka, 17, is emotional as she gets picked up by her mother after the school was evacuated following the shooting Comforting: Allie Zadrow (right) hugs her friend Liz Reinhardt (left) after being evacuated from the building All too familiar: Parents Cathy Thorson (left) and Heather Moran (right) hug each other after arriving on the campus to pick up their kids. Residents are all too aware that the Columbine High School massacre took place just eight miles away in 1999

Neighbors said that the high school senior ‘seemed normal’ and was described as being ‘sweet’ and ‘quiet’.

One neighbor told MailOnline that the boy was a member of the cross country team and they waved from across the street whenever they saw each other but were not particularly close.

To those who knew the boy, the fact that he had access to a gun does not come as a surprise as he reportedly showed his friends a picture of a shotgun that he used for hunting.

The timing and location of the shooting puts itself on a growing list of school shootings.

Sheriff Robinson said that while the investigation is still on-going, there is ‘absolutely no indication at all that this would be tied to Sandy Hook’ even though the shooting took place the day before the one year anniversary of the Connecticut shooting that left 20 children and six educators dead. Arapahoe High School is 16 miles away from the Aurora movie theater where a shooting occurred in June 2012 and only eight miles from Columbine High School, which was the scene of the first mass school shootings in the United States when it occurred in April 1999.

‘We are really, really, really surprised that this happened,’ senior Eric Waugh told CNN.

‘We had talked about it and we had lock down drills at times but we never thought that it would happen at our school.’ Escape: Law enforcement officers escort students, with their hands raised, out of Arapahoe High School Reunited: Students meet with their relieved parents at a fast food joint across from the high school Authorities swarmed the scene about 20 minutes after the initial call and t he sheriff commended the librarian for his quick thinking by leaving the school, saying that the man's intention was to get the gunman away from the school. 'In my opinion, this was the most important tactical decision that was made,' Sheriff Grayson Robinson said at an afternoon press conference. 'He took himself away from the school in an effort to get the shooter to go with him.'

Only one weapon, which was used in the shooting, has been found at the school.

Two other explosives- one of which was initially reported to be a Molotov cocktail- were found at the school. Sheriff Robinson said that one was smoking when police found it but it did not go off. The second explosive was disarmed before it went off.

He also specified that there are three scenes that are being searched in addition to the school: the shooter's car which was parked in the school lot, the shooter's home, and a secondary home that the shooter is believed to have had recent access to.

Lockdown: SWAT team members lead students away from Arapahoe High School near Littleton, Colorado Terror: The students kept their hands in the air where the gunman opened fire on Friday afternoon Staying together: Students from Arapahoe High School evacuate their building in Centennial My heart hurts so much right now for my alma mater #ArapahoeHighSchool "#Warriors always take care of each other." — AnnaSophia Robb (@robbannasophia) December 13, 2013 Authorities added that they believe the gunman acted alone but that this remains under investigation. They are searching Pierson's locker and visiting his home.

After news of the incident broke, hundreds of high school students were filmed running from Arapahoe High School in Centennial with their hands in the air shortly after gunfire broke out. As the situation unfolded at Arapahoe, all of the schools in Littleton, Colorado schools were put on lockdown.

'Am I going to get out?' one student told KDVR he thought. 'And if I do, what will happen when I get out?' He described frantic scenes inside the school when he and his classmates turned off the lights and locked the door. 'The teacher was trying to calm us down,' he said. 'A couple of people were crying. In the moment, we couldn't really think.' Another student, 15-year-old Whitney Riley, recounted fearful scenes to CNN, explaining that she heard one shot ring out, followed by two more. She said she ran to a room with classmates and a teacher, where many people were crying and one girl was biting her arm out of fear. She also credited her teachers with their brave response.

Scene: The school in Centennial is just eight miles from where the Columbine School shooting took place in 1999

Shooting: An aerial view of Arapahoe High School in Centennial, where police responded after midday