(CNN) -- It has become a tragically familiar scene in American life: law enforcement officers descending on a packed school where a gunman is on the loose. A procession of students, their hands raised, slowly making their way out of the danger zone.
But the handling of Friday's shooting at Arapahoe High School -- just 10 miles from the scene of the 1999 Columbine High School shooting where two students killed 12 classmates and a teacher before fatally shooting themselves -- drew important lessons from the earlier bloodshed.
At Arapahoe High School, where senior Claire Davis, 17, was critically injured before the shooter turned the gun on himself, law enforcement officers responded within minutes and immediately entered the school to confront the gunman rather than surrounding the building, authorities said.
As the sound of shots reverberated through the corridors, teachers immediately followed procedures put in place after Columbine, locking the doors and moving students to the rear of classrooms.
"That's straight out of Columbine," Kenneth Trump, president of National School Safety and Security Services, a Cleveland-based consulting firm, told CNN Saturday. "The goal is to proceed and neutralize the shooter. Columbine really revolutionized the way law enforcement responds to active shooters."
Arapahoe County Sheriff Grayson Robinson credited the quick police response time for the fact that student Karl Pierson, the gunman, stopped firing on others and turned his weapon on himself.
In fact, Robinson told reporters Saturday, Pierson killed himself less than 1 minute, 20 seconds after entering the school.
Robinson said a deputy sheriff assigned as a school resource officer and an unarmed security guard immediately closed in on the shooter. "That one minute and 20 seconds, in my mind, is extraordinarily relevant," he said, noting that Pierson was heavily armed, with ammunition, a knife and three explosives.
Authorities knew from research and contact with forensic psychologists that school shooters typically continue firing until confronted by law enforcement, Robinson said.
"We believe that the response from the school resource officer and from the unarmed school security officer was absolutely critical to the fact we did not have additional injury and or death," he said.
Robinson said the so-called active shooter response protocol, which was developed after Columbine, was put into place. In addition, school staff and students implemented a well-rehearsed lockdown practice.
"The combination of quick response by the resource officer and the implementation of a lockdown protocol caused the children and staff to be safe," he said. "Both protocols came together as they were designed to do."
Friday's shooting came on the eve of the one year anniversary of the Sandy Hook Elementary School massacre, where Adam Lanza killed 20 first-graders and six adults at the now-demolished elementary school in the second-deadliest school shooting in U.S. history.
"It's very unfortunate that we have to say that there's a textbook response on the way to respond to these, because that textbook was written based on all of the incidents that we've had and the lessons learned," Trump said.
Trump said both Sandy Hook and the latest shooting in Colorado highlight the importance of "training and engaging" school support staff -- from custodians to school secretaries to maintenance and food service workers -- on how to best respond during these incidents. In Sandy Hook, a school custodian's 911 calls provided authorities some of the first information about what was happening.
"Often these people are not getting training in school emergency planning," Trump said. "In a critical incident, they may be the first person to respond."
At Arapahoe High School, a school janitor spotted Pierson, whose intended target was a faculty member, in his tactical gear, he told CNN affiliate KMGH.
"It just looked weird," Fabian Llerenas said. "He went in, and I heard two pops. That's when I knew. I said, 'They are shooting in the school.'"
Llerenas said he called 911 and then escorted the targeted faculty member out of the school.
Pierson had fired at the man but missed, Llerenas told KUSA.
"He was so [shaken] up, he felt the wind hit, out of the shotgun just blew his hair, but it didn't hit him. It was that scary for him," Llerenas said.
"In my opinion, that was the most important tactical decision that could have been made," Robinson said. The faculty member "left that school in an effort to try to encourage the shooter to also leave the school."
Trump said other lessons learned from Columbine included the controlled evacuations and pat-down searches of students in a secure area. Self evacuations can create chaos for the police.
Additionally, schools now have predesignated parent-student "reunification centers" to prevent parents from showing up at the scene and interfering with law enforcement, as was the case in Sandy Hook, Trump said.
"The lessons of Columbine are still the best practices," Trump said.
After Sandy Hook. Trump said, some officials advocated a "run, hide or fight" approach developed for workplace shootings in which teachers and students are encouraged to be prepared to throw things at gunmen. Some even suggested that elementary school students use items such as cans of soup to attack gunmen. Trump called it a "high risk, high liability proposition."
"The good news is that we're getting better at preventing and responding to these incidents," he said. "The bad news is that there will be cases that slip through the cracks."