For the police, Columbine changed everything.

After two teens opened fire at a Colorado high school in 1999, killing 12 fellow students and a teacher before killing themselves, the police response to what they call an "active shooter" shifted dramatically.

"Columbine was like the case study for a change in police tactics," said Sgt. Mark Sanclemente, assistant commander of Manchester's SWAT team.

Until then, when a report came in for a gunman opening fire and "shooting innocents," Sanclemente said, the protocol was to "contain the situation and wait for a tactical component to arrive."

But what happened inside Columbine High showed that by the time a SWAT team gets to the scene, he said, "It's too late. It's over and done with."

Now, he said, every patrol officer in Manchester is trained to respond to such an incident immediately. "They don't wait," he said.

The protocol calls for at least two, preferably three, officers to be on scene before they go into a building where a shooter is at large, Sanclemente said.

Then, "For someone who's actually firing a gun, the officers are trained to go toward the gunfire and address the threat," he said. "The idea being that the police are armed, with training, with body armor, and you have a kid potentially who's not armed, who does not have body armor, who's hiding underneath a desk trying to save his own life."

In such a scenario, he said, "It's no longer acceptable to just sit and wait. That's what came out of Columbine."

And it's not only the big cities that are training this way.

Glen Drolet is police chief in Northwood and chairman of the training committee for New Hampshire Chiefs of Police Association.

His officers are trained to respond to an active shooter situation, and Drolet said it's the same in police departments across the state.

"It's not just the SWAT teams but the road officers that need to know how to handle something like that," he said. "You've got to get in there and do whatever you can to stop it, to save as many lives as you can."

And it sounds like that's just what police officers in Newtown, Conn., did after the first reports of a school shooting came in, he said.

For police here, Drolet said, what happened last Friday "is just going to reinforce how important that training is and how prepared we need to be."

The massacre of such young children is "incomprehensible," Drolet said: "To think that that could happen, that there's (someone) evil enough out there that could do something like that to children that age."

But he said New Hampshire residents can perhaps "take some solace" in the knowledge that police officers are trained to respond should the unthinkable happen here.

"They'll do what they have to do to end such an event as quickly as possible and to save as many lives as they can," he said.