walked into an office building in cincinnati and opened fire. several dead. tonight, his arsenal now revealed. abc's alex perez in cincinnati. >> reporter: the chaos unfolding in busy downtown cincinnati just as many were starting the day at work. >> multiple shooting victims. we have an active shooter. >> reporter: just after 9:00 a.m., authorities say the gunman, 29-year-old omar perez, opened fire in the loading dock area of the fifth-third bank building, striking several people. complete panic. >> everybody come running out of the bank, people in suits diving on the ground and stuff. shots fired. >> reporter: the gunman armed, investigators say, with a .9 millimeter semiautomatic pistol, multiple magazines and about 200 rounds of ammunition, then moved inside the building. >> there were gunshots exchanged. at this point, the shooter is deceased. >> reporter: three victims struck by the gunman killed. two others hospitalized. bullet holes and shell casings