From NBC Washington:
The shooter entered the building at 801 G Street NW [in the lobby of the Family Research Council, a conservative Christian organization] at around 10:45 a.m. Wednesday. He approached the front desk and said he was an intern before pulling a Sig Sauer 9 mm handgun from a backpack.
The guard confronted him, and they had an altercation before the shooter fired, striking the guard in the arm. Despite his injury, he gained control of the weapon and held it on the suspect.
Authorities found two loaded magazines with 15 rounds each in the suspect’s backpack, as well as Chik-Fil-A promotional materials, NBC4’s Jackie Bensen reported.