The tragedy in Connecticut has re-ignited the debate over whether the United States should ban assault weapons.
The school shooting has also created a renewed push to bring back the assault weapons ban that expired eight years ago.
"We ought to make sure we ban the assault weapons, limit the number of bullets in a clip, and prevent mentally ill people from getting guns," says New York's Senator Chuck Schumer.
In Connecticut this weekend, President Obama called for action.
"No set of laws can eliminate evil from the world, or prevent every senseless act of violence in our society. But that can't be an excuse for inaction. Surely, we can do better than this," he said.
Lawmakers say it will be first on their agenda in January.
Fearing new restrictions, gun enthusiasts are buying now, and stores are seeing record sales.
"Yesterday was the biggest day we've ever done in 20 years. Today will probably eclipse that," said Karl Durkheimer, owner of Milwaukie, Oregon's Northwest Armory gun store.
Opponents of gun control argue Connecticut already had tough gun laws, and so do other areas with high crime rates.
Lawmakers here are also calling for a national commission to examine mass shootings like the one in Connecticut.
Here in Colorado, residents across the state set a record for background check requests in a single day on Dec. 15, the day after the Connecticut shooting.
According to the Associated Press, more than 4,200 requests to buy guns were submitted, compared to the 4,028 requests on Black Friday this year.