A Tennessee man entered a dental office Wednesday morning and fatally shot his wife, who was employed at the facility, before he was shot and subdued by a patient waiting for treatment, the Knoxville News Sentinel reported.

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The incident was called in at David A. Guy Dentistry at 9:47 a.m., the Kingsport Times-News reported.

Sullivan County Sheriff Jeff Cassidy described the shooting as a “workplace” domestic violence incident, the newspaper reported. Cassidy also said the patient had a concealed weapon permit.

The identities of the victim and suspect have not been released, pending notification of kin. The identity of the patient is also being withheld, the News Sentinel reported.

"A concealed carry permit holder saw the threat, took action on the threat and stood by until officers arrived," Cassidy told the Times-News. "We're calling him a hero today."

The man accused of killing his wife was treated at a local hospital, the newspaper reported.