Police are praising the quick actions of managers at a campsite on the outskirts of Nelson who evacuated people after gunshots were heard.
The Armed Offenders Squad on Monday found the bodies of 53-year-old Thomas Hiki and Nicole Jean Barker, 50, in a caravan at the Maitai Valley motor camp.
The squad was called in by uniformed officers who were first to arrive.
Superintendent Gary Knowles says they found managers at the grounds had already begun evacuating campers.
ESR specialists will help with a forensic examination of the caravan on Tuesday.
Police are not looking for anyone else in connection with the deaths and the matter will be referred to the coroner.