It’s just little more than a wild guess, but possibly what led to the murder of the campus police officer was that having thought no one would ever be able to notice anything about them in that crowd, and suddenly seeing their photo released, the Terror Brothers were a little paranoid about the police being after them and thought the cop who was nearby in his car on his way to check on a noisy party was there for them.

Obviously if they did nothing but try to escape in the quietest way possible, they might have succeeded — no one had really identified the photo yet, although CNN reports that their relatives who saw the FBI photo in Russia recognized them immediately (to their horror).