Police in Princeton warned April 19 that a drone would be flying overhead in the coming days to take photos. The unmanned, remote-controlled aircraft — which looked like a toy helicopter, not a military plane — was hired by the University’s admission office to take video and photos for its publications. Police alerted residents because “we were concerned that if the public saw these drones in the air, they would be in a panic,” Princeton police Sgt. Mike Cifelli said. No panicked calls from residents were received, he added.