Activists lined up seven thousand empty pairs of shoes in front of the US Capitol building on Tuesday to represent children killed by gun violence in America since 2012.
Organisers want Congress to act on gun reform.
On Wednesday, US students will stage a nationwide school walkout calling for tougher laws on gun ownership.
It's part of the Enough! campaign that emerged after last month's shooting at Marjory Stoneman Douglas High School in Parkland, Florida.
Last week it seemed that President Trump was willing to tighten gun laws, but after a meeting with the National Rifle Association, he instead suggested he would press forward with arming school teachers.
Nineteen-year-old Nikolas Cruz has admitted to carrying out the Florida attack and is charged with 17 counts of premeditated murder.
Prosecutors have filed a notice saying they will be seeking the death penalty.