A paddock on their 250ha farm looked like a battlefield on Saturday morning, scattered with 111 dead and bloodied sheep.
Then, during a routine feed-out on Sunday, they discovered a further 80 hoggets had suffered the same fate overnight in another paddock.
Yesterday they were still finding sheep needing to be euthanised.
''It was gut-wrenching picking up so much stock and a lot of them still weren't dead. We had to cut a lot of their throats,'' Mr Stackhouse said.
''They'd been shot, but they were still standing there alive, or some had their legs shot off them.''
Initially, Mr Stackhouse thought the sheep had been attacked by dogs, but a second opinion from vet Luke Smyth confirmed bullet wounds.
Mr Smyth, neighbours and friends helped in the clean-up, which took several hours on Saturday and Sunday mornings.
No-one heard the sound of gunshots on either night, and motives remain a mystery.
Yesterday, Mrs and Mrs Stackhouse were fearful their property could be targeted again.
''The sheep were all scattered around the paddock. It was like an Iraq bomb site,'' Mr Stackhouse said.
There was no vehicle access to either paddock.
The Stackhouses have been farming on the North Otago property for about 20 years and have not had any problems with poachers or sheep rustling.
The Stackhouses run about 2400 sheep, and they had hoped to get about $30,000 from the lost stock, including in wool sales, in October.
A herd of 200 dairy cows in a neighbouring paddock was unharmed.
Fifteen calves in the same paddock as the hoggets on Friday night were not shot but were frightened and jumped a neighbour's fence.
Mr Stackhouse estimates the culprits spent more than $200 on ammunition. Detective Warren Duncan, of Oamaru, said police wanted to hear from anyone in the Ngapara area who saw anything suspicious or heard the sound of gunshots on Friday and Saturday nights.
''It's unusual, over two nights, and so many were killed,'' Det Duncan said.
The motive and what sort of firearm was used were yet to be established, he said.
