"He said every day when he'd come in, there'd be new stuff on the [bathroom] wall," Kristi Hannah told "Good Morning America."
"One was a hangman with a noose around his neck and underneath it said, "Kill the n-word.'"
Hannah, who said she was gunman Omar Thornton's girlfriend for nine years, said he showed her cell phone pictures of the racial slurs written in the bathroom.
"I know what I seen on that wall and that picture and that would make somebody go crazy," she said. "If they keep doing it to somebody over and over and over and over and over. And I know that was happening to him because no one just wakes up one day and does that."