The police found the white man, a student at the University of Maryland, at around 3:30 a.m. Saturday, sitting on a campus bench a few feet away from the spot where witnesses said he had plunged his knife into a black man’s chest.

The victim was pronounced dead sometime after 4 a.m., just three days before he was scheduled to graduate from nearby Bowie State University.

And amid inflamed anxieties about a rebranded white-power movement, the question that enveloped both young men’s campuses was why.

The authorities charged Sean C. Urbanski, 22, with assault and first- and second-degree murder in the death of Richard W. Collins III, 23, who had just been commissioned as a second lieutenant in the Army and was preparing to move to Fort Leonard Wood, Mo., for training in defending the country against chemical attacks.