In the initial chaos of these things, it seems like more than one shooter is almost always reported.
Washington Post claims to be quoting DC police in reporting 3 shooters. I note that 1 is described as dressed all in black, including black hat, and one in fatigues. But easy enough to take off fatigues.
Listening on my Iphone via the ap “I(heart)radio” to WMAL 105 FM/630AM.
Radio station is fairly non-emotional, stating that most news outlets not reporting multiple shooters.