"Their response was amazing," says Motyka. "Now it's a matter of figuring out what happened, and get 'lessons learned' from it."
But van Zandt says they still need to do more, particularly in identifying those with mental health issues, getting them treatment and reporting those who might turn to violent behavior.
"We need a checklist to determine, 'He is someone who needs help,'" he says.
Most attackers do not want to be held to the scrutiny of daylight, he adds, which is why they often kill themselves and take the cause of their anger with them.
"There is no one answer for anyone who tries to account for human behavior," van Zandt says. "We must have some way to identify people like [Lanza] as a person of risk."
Paul D. Shinkman is a national security reporter for U.S. News & World Report. You can follow him on Twitter or reach him at email@example.com.