It is rare for a gunman in a high-profile shooting to get away, and many are apprehended within days. The authorities shared grainy video and begged for tips as the search stretched into its fourth day.

© Providence Police, via Reuters

As a manhunt for a gunman who killed two and injured nine at Brown University stretched into a third day, residents and officials alike were growing weary.

© Christopher Capozziello for The New York Times