Lone Gunman, Karl Pierson, Dead In Colorado High School Shooting

A student with an apparent grudge against the debate coach barged into a Colorado high school Friday and terrorized his classmates for 14 minutes before killing himself with a shotgun blast.

Karl Pierson, is believed to have marched into the school calling out the name of his former coach before firing off several shots.

The gunfire erupted on the eve of the Sandy Hook Elementary School massacre anniversary and a few miles away from another Colorado high school where two students killed 13 classmates and themselves back in 1999.

But the only fatality this time was Karl Pierson, a senior student who police said wounded one student at Arapahoe High School in Centennial, Colo. Another student had an anxiety attack during the school evacuation and was taken to the hospital.

“There was absolutely no indication this was tied to Sandy Hook,” Arapahoe County Sheriff Grayson Robinson said. “The shooter that is deceased appears to be the lone actor in this tragic event.”

Police said the suspect  was armed with a shotgun and witnesses said he was targeting librarian Tracy Murphy.

“Where’s Murphy! Where’s Murphy!” the gun-toting student screamed as he ran toward the library, school custodian named Fabian Llerenas told local TV.

The student fired once and nearly hit Murphy, who managed to escape the building, Llerenas said.

"So when he did that he took one shot at him and missed his head, and he said he felt the wind just go up and down," the custodian said.

Murphy’s wife confirmed to The Daily News that her husband was safe, unharmed, and “currently locked in the back of a police car.” She declined to give her name.

Joe Redmond, 18, a senior captain on the speech and debate team and friend of Pierson, said the gunman was upset with Murphy after the school librarian kicked him off the team. 

“Karl half-jokingly threatened to kill Mr. Murphy, and Mr. Murphy got him suspended for saying that," Redmond told the Daily News. "Karl wanted to go to the Air Force Academy and they don’t look positively on suspensions so (Karl) felt like Mr. Murphy had ruined his life.”

Months after the snub, Pierson allegedly sought to take his revenge.

Police said he critically wounded a 15-year-old female student, who was taken to a hospital and undergoing surgery. 

Officials did not release either student’s names. But Robinson credited the targeted teacher with possibly preventing an even bigger tragedy.

“He took himself away from the school in an effort to try to encourage the student to move with him,” said Robinson, who called that move “the most important tactical decision that could be made."

Robinson said the shooter “made no effort to hide or conceal (the gun) as he entered the school.” The shooter had two devices that police identified as Molotov cocktails. Pierson set one off inside the school, police said, creating "a significant amount of smoke in the immediate area."

Asked about a motive, Robinson said “they clearly had a relationship.”

“The degree and level of that relationship is uncertain,” he said. "I guess revenge is the word that I choose."

Redmond described Murphy as "a saint, such a nice guy." But the teacher apparently pushed the wrong buttons for Pierson, who Redmond described as smart but "bombastic."

“He had a lot of very strong opinions," said Redmond, who knew the shooter for about three years. "He didn’t get along with people very well because his opinions were so big. He did not respond very well to the word no.”

In the aftermath, a profile of the shooter began to emerge — one that sounded all too similar to anybody with even a passing familiarity with the recent plague of school shootings across the U.S.

“He was kind of nerdy and geeky, but in a charming way,” a student named Frank Woronoff told the local FOX News affiliate. “I could see that he was bullied, but he was always humble and down to earth.”

The drama began at 12:33 p.m. local time when the gun-toting intruder entered the school from the west side and demanded to know where Murphy was, police and witnesses said.

Then three shots in succession ran out.

“We were all just sitting there staying quiet and praying," 15-year-old Jessica Girard, who was in math class when she heard the three loud bangs, told the Denver Post.

Girard said the next thing she heard was someone walk by her locked classroom door saying, “It hurts. It hurts. Make it stop.”

By 12:47 p.m., the danger was over and the nation was once again confronted with a case of gun violence in a school a day before residents in Newtown, Conn. were about the mark the first anniversary of the massacre that left 20 first grader and six school staffers dead.

Arapahoe High School is just eight miles from Columbine High School in Littleton, Colo., where two trench-coat clad students named Eric Harris and Dylan Klebold staged a massacre.

It's also about 20 miles from Aurora, Colo., where a crazed gunman named James Holmes opened fire in 2012 on moviegoers at the opening of the Batman movie “Dark Knight Rises,” killing 12 and injuring 58.