— SALEM, Mass. — When Adam Lanza slaughtered 20 first-graders and six staff members at the Sandy Hook Elementary School in Newtown, Conn., he used a Bushmaster AR-15 assault rifle to cause the carnage.
That's the same type of gun used to kill 12 people and wound dozens more in a July movie theater massacre in Colorado. It was used again this month to kill two people in a Portland, Ore., mall shooting.
This trilogy of killing sprees has ignited yet another national debate over the sale of semi-automatic weapons, with the AR-15 assault rifle front and center this time.
To many Americans, the AR-15 is a mystery. But not to the gun community. It is well-known there for its lightweight, durability and accuracy as well as the ability to fire multiple high-velocity rounds quickly.
Modeled after the U.S. Army's M-16, the user needs only to pull the trigger to fire each round after the weapon automatically readies itself to fire again from a high capacity bullet clip.
The rifle is commonly used by the public at shooting ranges, in marksmanship competitions and for hunting.
Lanza, the Connecticut killer, got the high-powered rifle from his mother, who had legally purchased it for shooting range practice. He murdered his mother before going to Sandy Hook School, and killed himself at the scene as police arrived.
That information has raised questions about what a military-style assault weapon with high-capacity ammunity clips is doing in a private home, accessible to a troubled family member.
But the AR-15 rifle, and versions of it, can be found in many homes across America.
Jim Wallace, executive director of the Gun Owners' Action League, estimated that "nationwide there's anywhere from 5 to 10 million of that rifle in the hands of lawful citizens."
He said gun owners consider it a popular "modern sporting rifle. We don't consider it an assault weapon."
That statement was borne out by the surge in sales of the AR-15 and similar semi-automatic rifles in the immediate aftermath of the Connecticut massacre because of fears the weapons may soon be banned by federal law.
Nick D'Augustine, owner of Milford Firearms in Milford, N.H., said he's setting sales records daily since the tragedy in Newtown.
"I've never seen anything like this," he said. "The phones been ringing nonstop, the cash register has been going nonstop."
Many of the nation's gun outlets said they could not keep up with the demand. Law enforcement agencies said they were deluged with orders for background checks on assault rifle buyers.
"We had to call in extra staff," Susan Medina, a spokeswoman for the Colorado Bureau of Investigation, told the Denver Post.
There's no certainty about how many Americans own guns. But a 2009 report by the Congressional Research Service estimated there are 310 million firearms in the U.S., excluding weapons on military bases. That's only 4 million short of the country's latest population estimate.
Past attempts to strengthen gun control laws have met with stiff resistance from the nation's gun lobby, contending banning weapons is a violation of the Second Amendment's right for citizens to bear arms. A 1994 federal ban on the sale of assault rifles was allowed to lapse in 2004 by President George W. Bush, and the U.S. Supreme Court struck down a strict gun control law in Washington, D. C., in 2008, citing the Second Amendment.
But this time even the National Rifle Association, the loudest voice in the pro-gun camp, says it is "prepared to offer meaningful contributions to help make sure this never happens again."
Members of Congress have said they will introduce legislation to reactivate the ban on assault rifles, and also to prohibit the sale of high-capacity gun clips that allow a shooter to unload a barrage of bullets quickly.
Additionally, President Obama said Wednesday he will create a task force, headed by Vice President Biden, to rein in gun violence. He said it should include new restrictions on guns, but also improved access to mental health services and better management of violence in popular culture.
"This is not some Washington commission.," Obama said at a press conference. "This is not something where folks are going to be studying the issue for six months and publishing a report that gets read, and then pushed aside. This is a team that has a very specific task: to pull together real reforms, right now."
Given the historic power of the American gun lobby, that likely will be a major challenge.
Details for this story were provided by the Salem, Mass., News and The Eagle-Tribune, North Andover, Mass.