A top police officer and three others were killed on Wednesday when their helicopter crashed in Nigeria\'s northern restive city of Jos. Deputy Inspector General of police John Haruna was carrying out surveillance with two other police officers over the city which witnessed a suicide attack at a church on Sunday. The four people on board, including the pilot, were killed in the accident, commissioner of police in Plateau Emmanuel Ayeni said. According to an eyewitness, the helicopter crashed into a house where a baby and few others were injured. \"The injured persons have been rushed to a hospital,\" he added.