Senior Superintendent Francisco Cristobal, city police chief, said the gunman, who remained unidentified, was accosted after the X-ray machine detected his firearm.
But instead of peacefully giving himself up, he tried to escape and fired at the pursuing port policemen, hitting PO3 Kadil Merced Lakibul, who died while being treated for multiple gunshot wounds in the hospital.
Port authorities said the gunman was to board a ferry bound for Basilan.
Police have tightened security at the port following intelligence reports that terrorist groups were plotting to bomb a passenger vessel. Roel Pareño