Activists left 7,000 pairs of shoes outside the U.S. Capitol on Tuesday to express the number of children’s lives lost since the devastating Sandy Hook shooting in December 2012, Mashable reports. 

The shoes were placed by the global activist group, Avaaz, to urge Congress to enact gun control laws after 17 people were killed on Feb. 14 at a high school in Parkland, Fla., according to Buzzfeed. 

Per Mashable, some shoes belong to families who lost their kids to school shootings across the country, as well as notable celebrities like Alyssa Milano.

The memorial is also meant to raise awareness for the student-led “March For Our Lives” rally on March 24.

The rally has gotten support from celebrities like Oprah, Dwyane Wade and Gabrielle Union.