The shooting was reported shortly before 6 a.m. on Tuesday, police said.
CNN  — 

An employee of a company that makes clear plastic teeth aligners opened fire at one of its Tennessee facilities Tuesday morning, injuring three people there before police officers shot and killed him, authorities said.

The gunman, identified by police as Antonio King, a 22-year-old day-shift employee, walked into the SmileDirectClub manufacturing facility in the Nashville neighborhood of Antioch just before 6 a.m. and shot a manager and two security guards, the Metropolitan Nashville Police Department said.

Security guard Johnny Hardin, 46, was being treated at a hospital in critical condition Tuesday afternoon; security guard Carlton Watson, 66, was in stable condition, police said.

Thomas Abbott, a 54-year-old manager, was treated at a hospital and released, police said.

The shooting happened during a shift change, police said. A worker who witnessed the shooting told CNN she had just clocked in and sat down at her station when she saw the gunman, weapon in hand.

“I immediately started taking cover,” Charlotte Jennings, 53, told CNN by phone. She said she saw him raise the gun and remembers him saying, “Why you running?”

At that point, he pointed the gun and started “spraying the place” with gunfire, Jennings said.

The MNPD investigation indicates that King initially fired his .45-caliber semi-automatic pistol with an extended magazine inside the facility without anyone being wounded, and then engaged in a shootout with security guards through the doors of the facility. According to MNPD, King fired more than 20 shots, during which the two security guards and a manager were wounded. Police believe King was also wounded by their gunfire.

Body-worn camera footage of the incident, released by MNPD, shows arriving officers repeatedly commanding King to drop his weapon, but receiving no compliance.

According to MNPD, Officers Dylan Ramos and Cherell Kinchloe then fired their weapons, fatally wounding King, who was declared dead Tuesday morning at Vanderbilt University Medical Center.

“The actions of Officer Kinchloe in firing two shots, given the vantage point represented by her video, are under review by the Police Department,” said MNPD spokesperson Kristin Mumford. “This investigation is in the early stages, and will take time to complete. In the coming days, the (Tennessee Bureau of Investigation) and the Davidson County District Attorney’s office will continue to analyze this incident.”

Mumford said by policy, MNPD will conduct a review of the tactics and interactions seen in the bodycam footage to ensure that they meet “the highest standards expected” of their officers.

Earlier, police said the gunman had shot two people. A fourth person injured her ankle while running, police spokesperson Don Aaron said.

‘The shots lasted so, so long’

SmileDirectClub said “the incident was contained quickly by security personnel on site.”

“The safety of our team members is a top priority for our company and we maintain strict security protocols and a no weapons policy at all of our facilities,” the company said Tuesday in a Twitter statement.

SmileDirectClub is known primarily for working with dentists and orthodontists to sell clear plastic aligners online as an alternative to traditional braces.

The shooting seemed to last for a long time, Jennings said.

“The shots lasted so, so long,” she said. “He let off a lot of gunfire.”

At some point, Jennings and others ran out a nearby exit.

“I never thought I would experience it on my job,” Jennings, a lifelong Nashville resident, said. “It was terrifying. I’m traumatized. It was just so scary.”

The gunman had started his most recent stint at the company in June, but also worked there from late 2019 to early 2020, police said.

The Antioch neighborhood is about a 12-mile drive southeast of downtown Nashville.

CNN’s Rebekah Riess and Carma Hassan contributed to this report.