Jared Loughner, 22, of Tucson is accused of the shooting spree that left six dead and a number wounded, including Rep. Gabrielle Giffords, D-Ariz.
In 2008, Loughner denied any involvement with the graffiti to a police officer, but in a second interview, told police the letters he had painted meant "Christian," The Arizona Republic reported Monday.
The newspaper said the officer wrote of the incident, "I asked Loughner the meaning of his moniker. He stated that the 'c' meant Christian and the 'x' also meant Christian," adding in parentheses, "As personally written by Loughner on my field interviewing notebook!"
The report said Loughner also admitted to other graffiti, always using a marker.
Loughner was driving a 1969 Chevy Nova Oct. 13, 2008, the Republic said, when a witness saw him get out of the car and write a symbol on a street sign. The witness got his license-plate number, the report said.
Records show the case was dismissed on Dec. 9, 2008, after Loughner completed a diversion program.
The Republic said court records indicate Loughner is 5 feet 10 inches tall, weighs 135 pounds and has blue eyes and brown hair.