I ARRIVED AT THE TRACE’S OFFICE in Brooklyn on the morning of October 2 to find one of our editors, Miles Kohrman, listening intently to a recording of Stephen Paddock’s attack hours earlier on the Las Vegas strip. Minutes later, Miles shared this note in our internal Slack channel: “Videos of the shooting show a really strange and inconsistent rate of fire. It almost sounds . . . bump-fired?”

It was a good hunch. A dozen bump stocks, which use a rifle’s recoil to simulate automatic fire, were found attached to weapons in Paddock’s Las Vegas hotel room. Our nonprofit newsroom was already familiar with the accessories — we first wrote about them in 2015. In the days that followed, we reported on how the products skirt the federal ban on new machine guns, and collaborated with The New Yorker on an animation showing how the devices work. Our reporting also helped inform other news organizations reporting on the attack.

Not every outlet got their coverage right. During a discussion of bump stocks, CNN aired a photo of a rifle equipped with a grenade launcher and silencer — but not a bump stock. Rightwing media, eager to unearth evidence that gun reporting by mainstream outlets is not to be trusted, quickly pounced on the inaccurate image.