encounter with officers. here s abc s alex perez. reporter: an investigation underway in nashville tonight after a horrifying shooting at this smile direct manufacturing facility tuesday, just as employees were changing shifts. authorities releasing this video identifying the gunman as an employee, 22-year-old antonio king. he seemingly was reporting for work, but with him, as he reported for work, was this glock semiautomatic pistol with an extended magazine and for some reason, he opened fire. reporter: frantic calls to 911 describing the gunman s rage. he s got multiple clips in his sling pack. because he keeps replenishing bullets. i probably heard 20 rounds. reporter: fellow employees terrified, scrambling for cover. we cleared the office area, and we re trying to clear people in the parking lot. people seeking shelter in between the vehicles. reporter: security guards in the building firing back, keeping king at bay, forcing him outside.