Sunday will mark 13 years since the Sandy Hook Elementary School shooting in Newtown, Connecticut, when 20 children and six staff members were killed.

Survivors, families and lawmakers gathered in Washington, D.C., on Thursday to honor the lives lost and continue calls for action to end gun violence.

"It took something from the ones who lived through it, too"

A Newtown High School graduate named Joshua spoke on behalf of his brother, who survived the horror inside Sandy Hook Elementary on Dec. 14, 2012.

"He was a first grader, a child, who should've been learning to read, making friends and drawing pictures, not fighting for his life," he said.

He added, "That day didn't just take lives of teachers and classmates, it took something from the ones who lived through it, too. It took parts of their childhood."

Their father, a police officer, was one of the first responders on scene, confronting the unimaginable in his own child's school.

"People like to say time heals, but they've never lived through the kind of aftermath we did," Joshua said.

Connecticut lawmakers call for assault weapon ban, Ethan's Law

Connecticut Rep. Rosa DeLauro said there have been 14,000 gun-related deaths so far this year and 387 mass shootings.

"In the 13 years since the Sandy Hook massacre, kids have grown up," Sen. Richard Blumenthal said. "This new generation is going to college ... They are our new generation of advocates."

He called for an assault weapon ban and the nationwide passage of Ethan's Law, a state law named for a Connecticut teen killed by an unsecured gun. The law requires firearms to be safely stored away.

"Congress needs to pass these bills," said a child from Brooklyn who lost her father to gun violence.

Advocates say tens of thousands of Americans lose loved ones to gun violence each year.