U.S. gun control activists called for expanded background checks for firearms purchasers and for a ban on sales to people on federal watch lists on Monday, in a protest marking the third anniversary of the massacre at a Connecticut elementary school.

Speakers including U.S. Representative Gerry Connolly, a Virginia Democrat, and survivors of recent U.S. mass shootings made their call outside the Fairfax, Virginia, headquarters of the National Rifle Association lobbying group. About 100 people attended the protest in the Washington suburb.

On Dec. 14, 2012, 20-year-old Adam Lanza shot and killed 20 first-graders and six educators at Sandy Hook Elementary School in Newtown, Connecticut, an attack that stands as one of the deadliest mass shootings in U.S. history. He began his attack by killing his mother at their home and ended it by turning his gun on himself.