A military-like response is essential to combat the spate of massacres at schools, theaters, malls and other public spaces in recent decades, experts say, along with a combined effort to identify would-be attackers before they lash out.
There are roughly 300 million privately-owned guns among the roughly 310 million Americans. Even if gun distribution ceased today, the quality of these weapons means that hundreds of millions of them could last for hundreds of years, says former FBI Agent Clint van Zandt.
Barring a way to eliminate access to weapons, communities must look to telltale predictors of violent behavior among troubled people like Adam Lanza.
"His mother knew, his teachers knew, his counselors knew," says van Zandt, a retired supervisor at the FBI's Behavioral Science Unit. "Everyone had a piece of the behavior, everyone had a piece of the puzzle, but they didn't come together."
There is no one event that drives someone to commit these kinds of crimes, says van Zandt. Rather, it is composition of factors, such as violent video games that reward simulated killing, an inability to resolve issues non-violently, and a society that must improve its ability to identify and treat mental illnesses.
Access to assault weapons with high-volume magazines is also a factor, he says.
Troubled people who then feel they are pushed to violent action often get ideas from previous massacres on which they model their behavior, van Zandt adds. Some want fame, others want to rack up a higher body count than previous killers.
Such issues contribute to a new trend of violence in recent decades, says Konrad Motyka, a current FBI special agent and president of the FBI Agents Association.
"This is somewhat new. It started in Columbine," he says, referencing the 1999 shooting at the Littleton, Colo. high school left 15 people dead and 21 injured. "These kinds of things, 20-30 years ago, they didn't happen. They're happening now."
"It looks as if there is an increase in these sorts of mass killings," he says. "They've definitely seen it on the rise, there's definitely a response to it."
This new response from police in recent decades applies a sense of immediacy, particularly for the kinds of crimes in which the attacker does not want to take hostages, says Motyka.
"[The] law enforcement response is almost a military one: You must get to the shooter immediately and take him down," he says.
The importance of this "mantra for law enforcement officers" made international headlines last year when lone-wolf shooter Anders Behring Breivik coordinated bomb and shooting attacks in Oslo and the remote island of Utoya, who avoided local police for almost an hour after they responded to the crimes.
But rural spread-out environments, such as Newtown, Conn., can complicate an immediate response.
"Unless you have an armed individual on site, the best you can do is to get there as quickly as possible," he says. "The reason [Lanza] stopped what he was doing and killed himself is because the police were there."
Motyka's comments echo an argument from gun advocates, who say that an attacker could be stopped if teachers were allowed to carry guns in schools. But he believes that logic would be too difficult to institutionalize in American culture.
"Practicing to engage in close quarters combat requires a lot of training," he says of schooling law enforcement officers receive. "That's not generally the mindset of people who teach six-year-olds, nor should it be."
"To train people who have a totally different focus—mental focus and purpose—that would transform our society in a way we don't want to go to handle these things," he says.
School staff should focus on a response that mirrors many teachers' clear thinking at Sandy Hook Elementary School, he adds. Many of them knew immediately to lock and barricade their doors and get their students into as protective a position as possible.