A common element links many of America's recent mass shootings: the presence of semiautomatic weapons in the arsenal of the shooters.
After a deadly rampage at a Colorado movie theater , an attack on an Arizona lawmaker and others, the mowing-down of Sikhs at a Wisconsin temple and the mass killings at Virginia Tech, law enforcement found at least one semiautomatic pistol in the possession of the killers.
And, on Friday, authorities said they seized two such weapons at the scene of the horrific slaughter at Sandy Hook Elementary School in Newtown, Conn., where 20 small children and six adults died.
SPECIAL REPORT: Connecticut school shootings
In all but one of those tragedies -- and in other earlier ones, including a mass shooting in Connecticut 15 years ago -- Glock semiautomatic pistols played a role.
The high-power capabilities of Glock pistols, as well as the ease of concealing them, attracts those bent on a high body count, according to criminal-justice experts. They are legally sold in gun shops and online, some for less than $500.
"Not only are semiautomatic pistols capable of rapid fire, they utilize high-capacity magazines and can be quickly reloaded," said a 2011 report -- titled "The Glock Pistol: A Favorite of Mass Shooters" -- by the Washington-based Violence Policy Center.
"The combination of these features makes semiautomatic pistols efficient killing machines," said the report.
Glocks of a variety of models and firepower are also the weapons of choice for personnel in more than 60 percent of U.S. law-enforcement agencies, according to industry data. They are accurate, relatively light and easy to shoot, and pack enough force to cut down threatening suspects.
Glock Inc., the Smyrna, Ga.-based U.S. branch of the Austrian weapons manufacturer, did not return a call for comment.
Among the U.S. mass killings in which Glocks were involved:
-- Friday's killings at the Connecticut elementary school, where police recovered a Glock and a Sig Sauer semiautomatic pistols, along with a .223-caliber semiautomatic rifle.
-- The July carnage at a midnight showing of a Batman movie in Aurora, Colo., where James Holmes is accused of killing 12 moviegoers and wounding dozens. Among other weapons, Holmes allegedly wielded a .40-caliber Glock handgun and had another in his car.
-- The January 2011 attack outside a Tucson, Ariz., grocery store that critically wounded then-Rep. Gabrielle Giffords and 12 others, and killed six. The convicted shooter, Jared Loughner, carried a Glock 19 pistol, police said.
-- The April 2007 mass shooting at Virginia Tech University in Blacksburg, Va., in which 32 students and others died, and 17 were wounded. Shooter Seung-Hui Cho, who killed himself, was armed with a Glock 19 pistol and a Walther P22 semiautomatic pistol.
-- The November 1999 deaths of seven at a Xerox office building in Honolulu, where Byran Uyesugi wielded a Glock 9 mm pistol.
-- The March 1998 rampage at Connecticut State Lottery headquarters, where Matthew Beck used a Glock 9 mm pistol to kill four and himself.
-- The October 1991 massacre at a Luby's Cafeteria in Killeen, Texas, where George Hennard used a Glock 9 mm, along with other handguns, to kill 23 and wound 20. Kennard killed himself as well.
A semiautomatic Springfield 9 mm pistol was the weapon of choice in August, when Wade Michael Page killed six and wounded four at a Sikh temple in Wisconsin. Page was shot to death by police.
And Anders Behring Brenik relied on a Glock 17 9 mm pistol, as well as a semiautomatic rifle, to mow down 69 people -- mostly teenagers -- at a youth camp in July 2011 in Norway.
Possession and manufacturing of all of these semiautomatic weapons in the United States are legal, but they largely had been banned for a decade after Congress and President Bill Clinton signed on to the Federal Assault Weapons Ban in 1994. But the law expired in 2004 under President George W. Bush.
President Barack Obama did not address a resurrection of that ban when he spoke about the Connecticut school shootings Friday, but he expressed support for some unspecified measures.
"We're going to have to come together and take meaningful action to prevent more tragedies like this regardless of the politics," Obama said, choking up during his statement.
U.S . Attorney General Eric Holder was in Tulsa Friday, and spoke on the Connecticut tragedy.
READ: Holder hints at gun control issue while in Tulsa (http://bit.ly/Holdershooting)