Police are searching for a gunman who shot dead two students and injured nine others at Brown University in Providence, Rhode Island. The attacker, described as a man dressed all in black, fled on foot. A shelter-in-place warning is in effect around the university. The shooting happened around 4 pm local time on Saturday in the Holley engineering building during final exams. An economics professor said the shooter came in yelling and started shooting during a review session. Two students in the nearby Rockefeller library stayed away from windows while waiting for police escort. Brown University is a prestigious Ivy League institution with over 11,000 students. Among the nine injured, one person is in critical condition, six are critical but stable, and two have less serious injuries. The victims' names have not been released. Brown University President Christina Paxson called the event “deeply devastating.” Police released CCTV footage showing a male suspect wearing all black with his face covered, walking away from the scene. The gunman’s exact identity is unknown and no weapon was found in the building during searches. Providence Deputy Police Chief Tim O'Hara said the suspect appears to be a man in his 30s. One person was arrested but later released after being cleared of involvement. About 400 officers and federal agents are now trying to find the suspect. Local residents and students have been told to stay indoors until the shelter-in-place order is lifted. US President Donald Trump called the shooting "a terrible thing" and offered prayers for the victims.