Colorado educators take part in a concealed carry course in Englewood, Colo., on Nov. 8. The course is open to all state school employees. Participants who complete the training are eligible to apply for a permit to carry a handgun. MATTHEW STAVER/Landov hide caption

itoggle caption MATTHEW STAVER/Landov

In 2010, Omar Thornton killed eight colleagues in Manchester, Conn., before killing himself. Private employers used to create their own rules about guns on their property. But over the past five years, many states have adopted laws that allow employees to keep firearms in their vehicles at work. Douglas Healey/Getty Images hide caption

itoggle caption Douglas Healey/Getty Images

Firearms for sale at a gun show in Annapolis, Md., on April 14. Andrew Harnik /The Washington Times /Landov hide caption

itoggle caption Andrew Harnik /The Washington Times /Landov

This AR-15 style weapon was on display in March at the 7th annual Border Security Expo in Phoenix, Ariz. It's among the type of weapons that advocates of new gun laws want to see banned. Joshua Lott /Reuters /Landov hide caption

itoggle caption Joshua Lott /Reuters /Landov

A Bushmaster rifle, similar to the type used by Adam Lanza during the shooting at Sandy Hook Elementary School, and some ammunition magazines. The sale and possession of this type of weapon, and high-capacity magazines, will be severely restricted in Connecticut under new legislation. Michelle McLoughlin /Reuters /Landov hide caption

itoggle caption Michelle McLoughlin /Reuters /Landov

After training, teachers and other staffers in South Dakota could choose to bring guns with them to school if their districts want to set up "sentinel" programs. Jim Urquhart /Reuters /Landov hide caption

itoggle caption Jim Urquhart /Reuters /Landov

Former Rep. Gabby Giffords, D-Ariz., and her husband Mark Kelly at Wednesday's Senate hearing about gun violence. Chip Somodevilla/Getty Images hide caption

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Neil Heslin brought a framed photo of himself and his son Jesse (when the boy was an infant) to Monday's hearing in Hartford, Conn. The 6-year-old was killed at Sandy Hook Elementary School in December's shooting. Cloe Poisson/Hartford Courant /MCT /Landov hide caption

itoggle caption Cloe Poisson/Hartford Courant /MCT /Landov

President Obama at the White House today, with Vice President Biden in the background. Mandel Ngan/AFP/Getty Images hide caption

itoggle caption Mandel Ngan/AFP/Getty Images

At a gun shop in Phoenix, a customer holds a handgun. Among the executive actions President Obama is expected to propose is an expansion of background checks for gun buyers. Ralph D. Freso /Reuters /Landov hide caption

itoggle caption Ralph D. Freso /Reuters /Landov

Shotguns sit on display at a gun show in Stamford, Conn., last week. Demand has risen for firearms as the White House prepares its new plan for gun control measures. New surveys find that a majority of Americans support some measures. Timothy A. Clary/AFP/Getty Images hide caption

itoggle caption Timothy A. Clary/AFP/Getty Images

Handgun barrels on the assembly line of Hi-Point Firearms in Mansfield, Ohio. Gus Chan/The Plain Dealer /Landov hide caption

itoggle caption Gus Chan/The Plain Dealer /Landov