The suspect, who has not been identified, reportedly entered Dr. David Guy Dentistry in Colonial Heights, Tennessee, on Wednesday morning.
Sullivan County Sheriff Jeff Cassidy described the shooting as a workplace violence and domestic violence situation.
Cassidy did not know what prompted the violence, but did confirm that the suspect and victim were husband and wife. The name of the victim has not been released.
A man with a concealed gun who was at the dentist’s office then shot the suspect, according to authorities, and controlled him until police arrived on the scene.
The suspect is now hospitalized with gunshot wounds, Cassidy said.
The name of the bystander, who Cassidy called a "hero," has not been released.
ABC News' Rachel Katz contributed to this report.