"We assume it is somebody in the house. The location of the graffiti seem to point to that," Epps said. "It's obviously someone who has deep-seated problems and wants to express them in some way."
But many house residents say they can't imagine that a Harvard student is behind the racial slurs.
"I wouldn't think at Harvard you would have such stupidity," Mather resident Marvin A. Coote '95 said Sunday.
The repeated nature of the incidents make the case unprecedented in recent Harvard history, according to Epps.
"You get the odd graffiti incident once a twice a year, but we've never had a pattern like this," Epps said.
After the latest incident, Mather residents and staff expressed an increased sense of frustration with their inability to identify the perpetrator.
"We all feed like we're being toyed with," said senior tutor Mary K. Peckham.