The encounter occurred at the home of Eric Wayne Dunphy, 54, and his wife after officials received a telephone call Sunday evening in which two people could be heard arguing. When Deputy Ronald Barba arrived at the home he was met at the doorway by Dunphy, who screamed he was going to kill his wife, Sheriff's Office spokeswoman Ginette Rodriguez said.
Dunphy then entered the home, put his wife in a headlock, held a tool to her head and threatened again to kill her, investigators said.
"It was a lethal situation, and that's when [Barba] fired his handgun," Rodriguez said.
Neither Barba nor the woman was injured. Authorities did not identify the tool Dunphy was holding or the name of the woman, the Orlando Sentinel reported Monday.
Rodriguez said Dunphy had previous arrests, and deputies had previously visited the home for domestic violence calls.