DENVER (KDVR) — On Sunday, flags throughout the United States are being flown at half-staff to pay tribute to some of the country’s bravest citizens who have put their lives on the line to shield their fellow Americans.

This is in observance of the annual National Fallen Firefighters Memorial Weekend, which includes a ceremony in Emmitsburg, Maryland. This event honors both volunteer and professional firefighters who have lost their lives in the line of duty over the past years.

President Donald Trump stated in a proclamation on May 1, “Every day across our nation, courageous men and women display acts of heroism, willingly putting themselves in danger for the sake of others. We owe a debt of gratitude to every American who chooses this honorable career — this solemn vocation — despite the inherent dangers involved.”

The proclamation notes the heroic efforts of firefighters on and after Sept. 11, 2001, as well as the destructive and deadly wildfires in southern California earlier this year. Trump also spoke of one firefighter whom he said will “forever hold a profound place in my life.”

“Corey Comperatore, who lost his life shielding his family from the barrage of assassin’s bullets that pierced the air during my rally last July in Butler, Pennsylvania,” Trump wrote in his proclamation. “His bravery and selflessness on that fateful day exemplify the dedication and courage that define America’s cadre of firefighters.”

Trump ordered that all U.S. flags be flown at half-staff at all Federal office buildings on May 3 and May 4. Governors throughout the country, including Colorado’s Gov. Jared Polis, have also ordered flags to be flown at half-staff, from sunrise to sunset, in alignment with Trump’s proclamation.

“This is a time to reflect and remember those and their families who have made the ultimate sacrifice to protect our communities in the face of devastating events. In Colorado, we value the hard work and dedication of our firefighters to make sure communities are prepared, protected, and informed during emergencies. We honor our fallen firefighters by ensuring their legacies and loved ones are cared for here in Colorado, ” said Polis in the announcement of his order.

Flags were previously flown at half-staff for about a week in April due to the death of Pope Francis.