Adelia Johnson says she briefly dated Connor Betts, the suspected guman who killed his sister and eight other people in Dayton on Sunday (August 4) morning.
The FBI has opened an investigation into the mass shooting.
On Tuesday (August 6) an official with the bureau said the gunman had a history of violent obsessions and previously mused about committing mass murder.
Johnson said that's not how she remembered Betts.
"He's not a monster, he did a monstrous act.
And if we just look at that, if we just label him as a monster, it's not gonna solve anything.
We're not gonna figure anything out," she told CBS.
Local media report that Johnson and Betts met in college and bonded over their mutual struggle with mental illness.
More than two dozen people were injured in the Dayton attack, which came 13 hours after a shooting spree that claimed 22 lives in El Paso, Texas.