No neighbouring landowners spoken to had given permission, and it appeared those involved were shooting from a vehicle on, or near, a public road.
Volunteers were often in and outside the fence, and were our "primary concern".
"We do after dark tours. There could be members of the public in here," Mr Baillie said.
Police were called, and while they did not catch those involved, a volunteer managed to speak to a person in connection with Monday's incident.
He said he had spoken with the two young male occupants of a 4WD in Mopanui Rd.
Both men were adamant they had permission to shoot in the area, but apologised for any alarm they may have caused, he said.
Police dispatched a patrol car, but did not find the vehicle involved.
District operations manager Inspector Dave Miller said the incident had the potential to be dangerous, and "good judgement is the key to using firearms safely".
Discharging firearm, airgun, pistol, or restricted weapon in or near a dwelling or public place was an offence under the Arms Act (1983).