BLOOMINGTON, Ind. -- The man accused of fatally stabbing an Indiana University professor told police the man had sexually assaulted him.

Michael J. Griffin, 25, of Bloomington, was arrested and preliminarily charged with murder on Tuesday in the death Don Belton, 53, an assistant professor of English at IU.

Police said they found the knife believed to have been used in the crime in Griffin's home.

When he was questioned, Griffin told police that Belton had sexually assaulted him twice on Dec. 25, and that he had gone to his house Sunday to confront him.

Griffin, an former Marine, told police he stabbed Belton several times with a 10-inch military-style knife when he failed to show any remorse.

Police said the two men were acquaintances, but not through Belton's work at the university.

Griffin's pleaded not guilty at his initial court hearing on Wednesday. He was being held without bond in the Monroe County Jail.

Belton taught at the University of Michigan and elsewhere before joining the IU faculty. His friends scheduled a candlelight vigil in his memory Friday night on Bloomington's courthouse square.