Lt. Kevan Toney said the shooter told police he saw the man strike a woman with an ax or hatchet inside a vehicle shortly after noon Wednesday on Nelson Avenue, just east of Lodge Avenue.
The neighbor intervened and shot the man, identified as Bernard Neyland, 59, of Toledo.
The woman, identified as Lakita Wilson, 53, of Toledo, suffered multiple cuts. She later received treatment for her injuries.
Neyland attacked Ms. Wilson with a hatchet when Benjamin Hand, a nearby resident, witnessed the assault taking place, police said. Mr. Hand then shot the assailant.
Neyland was taken to the University of Toledo Medical Center, the former Medical College of Ohio hospital, where he was pronounced dead at 12:55 p.m., said Dr. James Patrick, Lucas County coroner.
He suffered at least one gunshot wound in his shoulder. An autopsy is scheduled for Thursday.
Mr. Hand is being interviewed by detectives and the investigation is ongoing, police said.
Neighbors described hearing a gunshot and going outside, then seeing a man shot inside a white pickup truck. One man, who did not want to be identified, said the woman was screaming for help before the shooting.
He said he believed the shooter saved the woman’s life.