Staffers donned blue ribbons with a black stripe and observed a moment of silence Monday to mark the 13th anniversary of a 1998 attack on the Capitol, when a gunman stormed the building, killed two Capitol Police officers and injured a bystander.

A moment of silence was observed at 3:40 p.m. for Capitol Police Detective John Gibson and Officer Jacob Chestnut, who were killed July 24, 1998, by Russell Weston Jr., who had paranoid schizophrenia.

Speaker John Boehner’s (R-Ohio) office also dispensed blue ribbons with a black stripe to commemorate the anniversary.

In a floor speech, Senate Minority Leader Mitch McConnell praised the slain officers, who are honored with a plaque inside the Memorial Door leading out to the East Front.

“It was 13 years ago that Officer Jacob Joseph Chestnut and Detective John Michael Gibson made the ultimate sacrifice to protect all who were working and visiting the Capitol on that Friday afternoon,” the Kentucky Republican said. “Every year at this time, we take a moment to step back from our work, put aside our differences and remember these good men whose sacrifice stands as a permanent reminder of the debt we owe to them, and to all those who continue to put themselves on the front line every day to defend the rest of us — from the Capitol Police force, to local law enforcement officials, to those serving overseas.”