The reporter who exposed Virginia Gov. Ralph Northam’s racist yearbook photo said a “concerned citizen” led him to the story that has prompted widespread outrage and calls for the Democrat’s resignation.

Patrick Howley, editor in chief of the website Big League Politics, first reported Friday the existence of a photo on Northam’s page of his medical-school yearbook depicting a figure in blackface standing next to another person in a Ku Klux Klan hood.

“It’s very easy to explain,” Howley, 29, said in an interview on Saturday. “A concerned citizen, not a political opponent, came to us and pointed this out. I was very offended [by the photo] because I don’t like racism.”

Paul Farhi, writing for The Washington Post, has the story about the story that will likely bring down Virginia Governor Ralph Northam — and how it came to be.