In the shadow of the Capitol, an emotional tribute to child victims of gun violence took an unorthodox format: Thousands of shoes.

All in all, 7,000 pairs of shoes lined the lawn, representing each of the children killed by guns since the Sandy Hook massacre in 2012.

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The event was planned by Avaaz, an international advocacy group, that has done similar events before. In 2015, they lined up thousands of shoes in Paris in a protest for climate change action. Shortly after the Parkland shooting, the group set up a trio of billboards, near Marco Rubio's Florida headquarters.

The group bases their estimate of 7,000 child deaths on a study by the American Academy of Pediatrics, that broke down CDC numbers. That report found that approximately 1,300 children are killed by guns each and every year. That breaks down to 3.5 killings each and every day.

A Call For Action:

Among the thousands of shoes, a pair of turquoise blue cowboy boots stood out. Next to it was a photo of Allison Parker, the 24-year-old reporter, who was shot and killed on live TV in 2015. Her parents looked at the boots with a mix of grief and nostalgia.

"You can just remember her smile," she her mother, Barbara. "It could just light up the room."

The Parkers were among the dozens of volunteers, calling on Congress to take action. Together they held up a sign that read "#NotOneMore," indicating that no more children should have to go through the pain, caused by gun violence.

Lori Haas was also there, speaking with WUSA9 about her painful memories. Her pursuit of gun control all began in 2007, when she received a devastating phone call from her daughter, who was studying at Virginia Tech.

"I remember getting the phone call from Emily the morning of April 16th," she said. "And she said 'hi mommy. I've been shot.'"

Fortunately that phone call would not be their last. Her daughter survived the shooting. Since that day, Lori has been calling on Congress to take action.

"The numbers are so gross in this country," she said. "Any other cause of this carnage would be pounced on by the Congress.. It's a moral failing on their part."

The display was kept on the mall until 2 p.m. Tuesday afternoon.