Colorado has become a focus point in the national debate over what new laws, if any, are needed to prevent gun violence in the wake of recent mass shootings, including an attack at a suburban Denver movie theater last summer - a massacre that brought to mind the Columbine High School shooting of 1999 for many in the state and across the nation.
Lawmakers in the politically moderate state are considering a package of gun control measures, including plans that would limit the size of ammunition magazines and expand background checks to include private sales and online purchases.
Retired astronaut and Navy captain Mark Kelly told lawmakers that he and his wife support the Second Amendment, but he said the right to bear arms shouldn't extend to criminals and the mentally ill.
"When dangerous people get guns, we are all vulnerable," Kelly said.
Kelly has testified before Congress in support of gun control measures. Giffords, a former Democratic congresswoman from Tucson, Ariz., was severely wounded in a mass shooting in January 2011 while meeting with constituents.
Gun control opponents say the proposals will not reduce violence. They say lawmakers should focus on strengthening access to mental health services for people who could be dangerous to communities.
The commotion at the Capitol underscored the attention the debate has generated nationally from gun rights groups, such as the National Rifle Association, to victims' families and White House officials.
There were so many people at the statehouse that an audio speaker system was set up outside so dozens of gun rights supporters waiting to testify could follow the hearings.
Several bills before state senators already have cleared the House. And because Democrats control both chambers of the state Legislature, the proposals have a strong chance of passing. The state's Democratic governor, John Hickenlooper, supports magazine limits and expanded background checks. He hasn't indicated whether he supports a proposal that would hold sellers and owners of assault weapons liable for shootings by such firearms.
The package of bills is expected to keep lawmakers at work late into the night.
During a Senate hearing, Kelly compared the different background check requirements for private and retail sales to having two different lines at the airport, one with security and one without.
"Which one do you think the terrorist is going to choose?" he asked.
Gun rights supporters, meanwhile, arrived wearing stickers that read, "I Vote Pro-Gun." Several dozen people outside the Capitol waved American flags as light snow fell, and a small plane flew overhead carrying a banner with a message for the governor, "HICK: DO NOT TAKE OUR GUNS!"
One of the nation's largest producers of ammunition magazines, Colorado-based Magpul, has threatened to leave the state if lawmakers restrict the size of its products. Its founder said smaller magazines can be easily connected to each other and the company fears it would legally liable if people were to do that.
Victims who have lost relatives to gun violence say it's time for legislators to take action.
"It's for those who still have children and are going to be attending schools. It's for those who go to church on Sundays. It's for those who go to the mall," said Dave Hoover, the uncle of 18-year-old AJ Boik, one of 12 people killed in the Aurora, Colo., theater shooting.
Senate Republicans have gotten thousands of emails from supporters of the Second Amendment, urging them to vote no on the bills. In one email provided to The Associated Press, one woman wrote to a senator that she worried that lawmakers would be taking freedoms from her children.
"Please don't take even a tiny aspect of their freedom from them by passing legislation that in the end can't stop bad people from making bad decisions," the woman wrote.
Jane Dougherty, whose sister, Mary Sherlach, was a psychologist killed in the shooting rampage at Sandy Hook Elementary School in Newtown, Conn., has been lobbying Colorado lawmakers to pass new gun laws. She said she doesn't understand gun owners who worry the bills are putting a burden on their rights.
When you lose a loved one to gun violence, "your life is never the same," Dougherty said. "All these lives are changed by a gun in the wrong hands. That's the burden, and we can't lose sight of that."
Associated Press writer Kristen Wyatt contributed.
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