Tasmanian police last night were still trying to negotiate with the gunman holed up in Seascape, a small timber cottage near Port Arthur.
Police spokesman Geoff Easton told AAP: "They are attempting to negotiate the man out."
Meanwhile, a major trauma counselling centre for Tasmanians who had friends or relatives at Port Arthur yesterday afternoon was being set up at the Rokeby Police Academy, on Hobart's Eastern Shore.
Mr Easton said trauma counselling teams were also at Port Arthur.
"They are at the site for not only the visitors but staff at the site," he said.
Mr Easton said the previous three hotlines for those who had friends or family at the site had now been replaced by a single number with eight lines.
Those wanting information about people who may have been at Port Arthur should call 002 30 2677.