Colo. school shooter had shotgun, machete, 3 incendiary devices: sheriff

ABOVE: Investigators seeking answers to shooting by 18-year-old high school senior

CENTENNIAL, Colo. – A sheriff says a teenager who opened fire Friday at a suburban Denver school, wounding a fellow student before killing himself, entered the school with a shotgun, machete and three incendiary devices in his backpack and had ammunition strapped to body.

Arapahoe County Sheriff Grayson Robinson says 18-year-old Karl Halverson Pierson, a senior who participated in debate activities, bought the gun legally at a local store Dec. 6.

Robinson says the shooting likely was motivated by retaliation against a faculty member, probably a librarian.

Anyone over the age of 18 is allowed to buy a shotgun in Colorado. Only those over 21 can legally buy a handgun.

The event sent a chill through a state that’s still trying to make sense of mass shootings at Columbine High School and an Aurora movie theatre.

Quick-thinking students at Arapahoe High School on Friday alerted the targeted teacher, who quickly left the building. Police immediately locked down the scene on the eve of the Newtown massacre anniversary – a sombre reminder of how commonplace school violence has become.

Within minutes, the 18-year-old shooter was dead, apparently of a self-inflicted gunshot wound.

The wounded classmate, a 15-year-old girl, was in critical condition with a gunshot wound, Robinson said. Two other students were treated for minor injuries and released.

Authorities evacuated hundreds of students in an orderly procession – a demonstration of aggressive security measures developed by police and schools following the chaotic 1999 shooting at Columbine, some eight miles west of Arapahoe High.

After that tragedy, police across the country developed “active shooter” training in which responding officers rush toward gunfire – and step over bodies and bleeding victims if necessary – to stop the gunman.

“The first deputy sheriffs and police officers that were on scene immediately entered the school to engage the shooter if they could locate that individual and keep the other students safe,” Robinson said.

“This kid, the officers went right to him literally within minutes,” said Gov. John Hickenlooper. “That is a world of change from the way response used to happen.”

Before Columbine, officials followed a contain-and-wait strategy in which arriving officers set up a perimeter to contain the situation, then wait for SWAT team members trained in military tactics to bring down the gunman.

Robinson said Pierson made no attempt to hide his weapon while entering the school from a parking lot and asking for the teacher by name.

When the teacher learned that he was being targeted, he left “in an effort to try to encourage the shooter to also leave the school,” Robinson said. “That was a very wise tactical decision.”

Students heard shots and cowered in classrooms while awaiting word on what had happened.

Senior Megan Jeffords, 18, was singing Christmas carols in the hall with her choir class when the shots rang out. A teacher rushed the 18 singers into a closet, where they huddled for more than half an hour.

Hours later, after Jeffords was reunited with her father, she was still visibly shaken and unable to talk much about what happened.

Jessica Girard was in math class when she said she heard three shots.

Timeline: Deadly U.S. shootings since Newtown

“Then there was a bunch of yelling, and then I think one of the people who had been shot was yelling in the hallway, ‘Make it stop,”‘ she said.

Two suspected Molotov cocktails were also found inside the school, the sheriff said. One detonated, though no one was injured.

The shooting came a day before the anniversary of the Newtown, Conn., attack in which a gunman killed 20 children and six adults at Sandy Hook Elementary School.

Since Columbine, Colorado has endured other mass shootings, including the killing of 12 people in a movie theatre in nearby Aurora in 2012. But it was not until after the Newtown massacre that state lawmakers moved to enact stricter gun control laws.

Two Democratic lawmakers were recalled from office earlier this year for backing the laws, and a third recently resigned to avoid a recall election.

Associated Press writer Ivan Moreno contributed to this report.