President Obama is set to give his last State of the Union address to a joint session of Congress tonight.

Every year, guests enjoy invitations from members of Congress and other branches of government, including the White House. Last week, the president announced a symbolic gesture of leaving one of First Lady Michelle Obama's guest seats empty to honor "the victims of gun violence who no longer have a voice," the White House said.

The Huffington Post published a defense of Obama's action written by Lonnie and Sandy Phillips. They're the parents of Jessica Ghawi, who died in a mass shooting at a movie theater in Colorado in 2012.

"The White House arranged to leave an empty chair in the gallery. That empty chair represents our loved ones taken by gun violence. It symbolizes the sudden loss and enduring suffering and resolve that each of us who have had a loved one taken by gun violence understand all too well,"   they said.

In the lead up to Obama speech, social media flooded with pictures people say have been lost to gun violence in America using the hashtag #EmptySeat.