F/S Forster had been in the air force for 27 years and was an expert in explosive ordinance disposal , AVM Lintott said.
The EOD squadron disposed of conventional explosives, along with chemical, biological, radiological and improvised explosives, as well as commercial ammunition and explosives.
F/S Forster had returned from Afghanistan, after working in explosive ordnance disposal with the provincial reconstruction team in Bamiyan province.
The shell which killed him had a lethal range of about 50 metres, and the shrapnel had a range of up to 250 metres, AVM Lintott said.
The two men were metres from the shell, " so the other chap is extraordinarily lucky to get away with his life, let alone superficial injuries".
AVM Marshall said marking unexploded shells was a routine process which all army personnel were trained to do.
The unexploded shell had been discovered yesterday afternoon but the personnel who found it did not have appropriate equipment to mark it, so returned this morning.
" It was during the process of putting the stake in the ground near the shell that it seems to have exploded and killed Flight Sergeant Forster."
The Defence Force was supporting F/S Forster's family, which included his wife and three children.
The army had begun an investigation into the explosion, and the Defence Force was working with the police and had notified the coroner's office, AVM Lintott said.
Defence Force Minister Wayne Mapp earlier told reporters F/S Forster's tri-service squadron received "a very high level of training but it is an inherently dangerous job".
"Everyone volunteers for it."
Labour leader, and former Defence Minister, Phil Goff said he was well aware of the dangers military personnel face every day.
"Our military personnel know these dangers but that does not lessen tragedies such as the one that occurred today.
"My heart goes out to the families and friends of the victims of the explosion," he said in a statement.
- NZPA
