A student opened fire at a high school in Centennial, Colorado, critically injuring a classmate before apparently taking his own life. The school is located down the road from the Aurora movie theater where a gunman went on a shooting spree in 2012.

The victim of Friday’s shooting is a 15-year-old girl, who remains in hospital after surgery. Another female student was thought to be injured as well, but was actually spattered with the victim’s blood.

The shooting was reportedly triggered by a grudge towards a member of staff over a demotion in a debate team.

The Denver Post reported that a shooting had occurred at Arapahoe High School around 1:00 p.m. local time. One hour later, it was announced during a press briefing on the scene that the suspect had been found dead inside the school, apparently from a self-inflicted gunshot wound.

Authorities reported evidence of two Molotov cocktail at the scene. Arapahoe County Sheriff Grayson Robinson told reporters that investigators were working on examining the device, and had found remnants of the two devices, one of which was apparently detonated. They believe that the gunman came armed with a shotgun.

Students heard multiple shots coming from the cafeteria around lunchtime, Post reporter Ryan Parker tweeted from outside the school, just moments after the incident unfolded.

Students tell me they heard multiple shots coming from the cafeteria. Everyone ran out of school. — Ryan Parker (@ryanparkerdp) December 13, 2013

Students are telling me at least two students were shot by another student in the cafeteria. #ArapahoeHighSchoolpic.twitter.com/PQ3U3fTCp1 — Ryan Parker (@ryanparkerdp) December 13, 2013

The shooter, identified by several news outlets as Karl Pierson, 18, wanted to confront Tracy Murphy, the school’s librarian and head of its debate team. ABC 7 in Denver reported that Murphy had recently kicked Pierson off the team.

Murphy escaped the school uninjured before being approached, law enforcement said. The sheriff also stated it was a smart decision for the teacher to run out of the school in an attempt to lure the shooter away from the building.

The first person to see the Pierson and notify the police was a school janitor, who told KUSA he only wished to be identified as Fabian. He said the gunman appeared to be running from side to side in the building in what appeared to be some “kind of military style.”

“I looked to see if there was a gun. It was a shotgun,” Fabian said. “When he went into the library, he said, ‘Where is Murphy?’”

One student of around 15 or 16 years of age was admitted to a local hospital with a gunshot wound, Denver's 9News reported. The student was in critical condition following surgery, while another student had earlier been reported as being hurt but had actually been covered in the first victim's blood and was unharmed, reported the AP.

Around 40 minutes after the first reports surfaced, Parker added that eyewitnesses told him students were still locked inside the school's classrooms.

Adam Jones, whose sister goes to high school, said students are still locked in rooms, and "very scared" #ArapahoeHighSchool — Ryan Parker (@ryanparkerdp) December 13, 2013

Jordan Steffen of the Post added that the students she interviewed outside the school heard three or four shots fired before they fled the building.

Students are gathering across the street. They say they heard 3/4 shots before they turned off the lights and crouched on the floor. — Jordan Steffen (@jsteffendp) December 13, 2013

More than 2,100 students are enrolled in the school, which is located in the center of Centennial. It is a half-hour drive from both Denver and Aurora, and located just 15 miles from Littleton - where two high schoolers opened fire at Columbine High School in 1999, murdering 12 students and a teacher.

All Littleton public schools were placed on lockdown as police responded to the incident at Arapahoe High. That order was later lifted once Pierson was found dead after a self-inflicted gunshot, and students were released to throngs of waiting parents.

Friday’s incident occurred 364 days after a shooter in Newtown, Connecticut went on a rampage at an elementary school, killing more than two dozen.

Arapahoe High contains 70 classrooms and encompasses around 254,000 square feet.

SWAT team leading students away from #Arapahoe High School. Latest information here: http://t.co/Na1znGsgLSpic.twitter.com/m2GPyLSiAB — KDVR FOX31 Denver (@KDVR) December 13, 2013

The shooting once again raises the issue of gun control in the United States, where despite the bevy of gun violence and outcry for stricter laws limiting the proliferation of firearms, resistant politicians have blocked such measures. Supporters of more legal restrictions point to the powerful gun lobby as the puppetmaster behind Washington’s inaction.

“They frighten politicians from doing the right thing,” Leah Gunn Barrett, director of New Yorkers Against Gun Violence, told RT. “The politicians are more in the back pocket of the corporate gun lobby than in the interests of their constituents.”

Gunn Barrett said the current approach by gun control advocates may be too narrow, and that the numerous deaths and injuries from firearms is a major public health problem that must be addressed.

“When you have 31,000 Americans dying every year from guns and 80,000 being injured, that’s a public health crisis. So you need to apply a different approach. It’s been successfully done with, for example, automobiles and tobacco smoking. You look at how you can address death and injury from the product. And there are two ways you can do that: You can strengthen our laws, federally and state, through education. Plus, you can make the product safer, and the gun industry has resisted any attempt to make their product safer. Smart gun technology is out there, but you’re not seeing them investing in it.”