(CNN) Dozens of students and activists lay still on the lawn of the US Capitol for 12 minutes Tuesday at an event they hoped would focus attention on gun violence.

Organizers behind the event -- National Die-In Day -- said those 720 seconds symbolized the approximate number of people killed in mass shootings in the United States since the Pulse nightclub massacre on June 12, 2016, in Orlando, Florida.

Prior to the protest, a succession of speakers had pleaded with legislators to pass measures that would bring meaningful reform of gun ownership laws. A number of the speakers said they were themselves victims of gun violence.

One of those standing on the podium, 18-year-old Bree Butler, is a survivor of a mass shooting at her school. Her senior year at Santa Fe High School came to a horrifying end on May 18 when Dimitrios Pagourtzis opened fire and killed eight students and two teachers.

"This is the most important thing, for my life ... I have a life because of this movement," said Butler, wearing a hoodie and a "Survivor" button.

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