Matthews was ready to express the pain and outrage he was feeling.
To set the scene, Matthews, his brother Ashton and a friend taped a smoke grenade to the white facade of the building. Ashton then stood in front of the smoke grenade, which was spewing red fumes; the friend, who is white, held an airsoft gun to Ashton's head. Matthews snapped the scene, and the result was stunning.
"Once I saw the pictures on the back of my camera, I knew that there would be some sort of an impact. My only issue was, when do I put the image out?" recalls Matthews, who wanted to gain the widest possible audience. "I had to time it correctly."
Four days later, on May 25, 46-year-old George Floyd died after a Minneapolis police officer put his knee on Floyd's neck for nearly nine minutes.
That night, after learning of Floyd's death, Ashton texted his brother: "It’s time."
After he shared the series of images on social media, Matthews received extensive praise for them. "Everyone has loved it," he says. But it's been the physical version of one of the photos, printed onto posters, that has had the biggest impact.
As protests started gripping downtown Denver last week, Matthews began printing out the image on posters and handing them out. Now you can spot the image at every rally in Denver, day or night. "They’ve all wanted to carry it around. They’ve all wanted to show love for it," Matthews says.
The striking image is complex. For Matthews, there's the obvious symbolism of an African-American male being shot in the head while clearly labeled "unarmed." But there's also the swallow tattoo, a sign of peace and love, on the arm of the shooter, which represents "the betrayal of America to its people of color," he says.
And then there's the lack of blood on the hand of the shooter, which shows "how black people feel the American government and white people refuse to let the blood be on their hands," Matthews explains.
"These police killings and hate crimes were swept under the rug for so long," he adds.
Smart Tees, which is selling them for $30; 15 percent of each sale is being donated to the Colorado Freedom Fund and the Minnesota Freedom Fund.) In addition to giving away the posters and shirts, Matthews plans to continue posting the image to social media until society changes for the better.
"I vow to share the image every Monday, every week, until legislation is passed and justice is served — not only for the cop who kneeled on George Floyd, but the three others and all the other corrupt cops in this country," Matthews says.
On June 3, Derek Chauvin, the Minneapolis officer who'd pressed his knee into Floyd's neck, was charged with second-degree murder after previously being charged with third-degree murder and second-degree manslaughter; the three other officers who were on the scene were charged with aiding and abetting. Months after Arbery's death, Gregory McMichael and Travis McMichael, father and son, had been charged with felony murder on May 7; William Bryan, who'd filmed the shooting, was charged with felony murder on May 21, the day Matthews took his photographs.
While the protests continue and these cases, along with others involving police brutality, go through the courts, Matthews plans to keep sharing the image across the nation and even around the world.
"People are asking for the high-resolution images in other places so they can print them on posters," Matthews says. "I got a picture from Dublin, Ireland, of someone with a sign with that picture on it. I was mind-blown."