March for Our Lives (MFOL), the gun safety group founded by student survivors of the 2018 massacre at a Parkland, Florida, high school, said it has planned more than 450 rallies for Saturday, including events in New York, Los Angeles and Chicago.

The organization's 2018 march on Washington, weeks after 17 people were killed at Marjory Stoneman Douglas High School in Parkland, brought hundreds of thousands of people to the nation's capital to pressure Congress to take legislative action, though Republican opposition has prevented any new limits on guns from passing the U.S. Senate.

This year's event in Washington has a simple message to political leaders, according to organizers: Your inaction is killing Americans.

"We will no longer allow you to sit back while people continue to die," Trevon Bosley, an MFOL board member, said in an emailed statement.

A gunman in Uvalde, Texas, killed 19 children and two teachers on May 24, 10 days after another gunman murdered 10 Black people in a Buffalo, New York, grocery store in a racist attack.

The latest mass shootings have added new urgency to the country's ongoing debate over gun violence, though the prospects for federal legislation remain uncertain.