"It’s time," says the group Demand a Plan. "Join more than 750 mayors and 750,000 grassroots supporters to demand that President Obama and Congress step forward with a plan to end gun violence."

Here's what they want:

- Require a criminal background check for every gun sold in America
- Ban assault weapons and high-capacity magazines
- Make gun trafficking a federal crime, including real penalties for “straw purchasers”

And they make it easy for you to press these demands by e-mailing or calling your members of Congress and your president.