KARACHI A policeman was killed and three others including DSP of Sohrab Goth got injured during an exchange of fire with land grabbers here at Superhighway on Wednesday. Police said that on the directive of Sindh High Court (SHC), police tried to initiate operation against land mafia to evacuate seven acres of encroached land of Aligarh Society located near Ahsanabad Police Post in the limits of Sohrab Goth Police Station.