One gunman has been killed and up to two more may still be at large after a shooting rampage at the US Naval base in Washington on Monday that left \"multiple victims\" dead, the city\'s police chief said. \"We have one shooter that we believe involved in this that is deceased,\" said Washington police chief Cathy Lanier. \"The big concern for us right now is that we potentially have two other shooters that we have not located at this point.\"