Police were called to the property, near Wedderburn and about 210km from Melbourne, about 8.30pm on Wednesday after reports of a minor dispute between neighbours.

Fairfax Media can confirm that Peter Lockhart, president of the Wedderburn Historical Engine and Machinery Society, his wife Mary Lockhart, and Mrs Lockhart's son Greg Holmes died on Wednesday night.

On Thursday morning, Detective Superintendent Peter De Santo said when police arrived at a Mulga Ridge Road property, they found a dead body in a paddock on the adjoining Wedderburn-Logan Road before hearing gunshots.

"Police arrived and found one person deceased in a paddock ... before they heard gunshots from an adjoining property across the road," Detective Superintendent De Santo said.

Police then made contact with the suspect over the phone, marking the beginning of a three-and-a-half hour siege which initially forced police to withdraw for safety reasons.

"[W]e had contact from a suspect, who was indicating he had been involved in the incident," police said on Wednesday night.

"The suspect contacted the police on the phone, and we were aware of other firearms being used."

The man eventually surrendered peacefully and was taken into custody. The arrested man is 63 years old and was assisting police with their inquiries on Thursday morning.

After the standoff, police found two more bodies - one in the driveway and one at the rear entrance - at the house across the road, Detective Superintendent De Santo said.

The bodies are believed to be that of a couple in their 70s and their son, a 48-year-old man.

The arrested man has been treated for a medical issue at Bendigo Health hospital.

The man arrived at the hospital mid morning and left the hospital's emergency department about 12.25pm.

While the families have had a history of minor disputes, there was no indication of "major domestic violence or ongoing assaults between these people", Detective Superintendent Peter De Santo said.

Detective Superintendent De Santo said the dispute was "at the very bottom end of disputes between neighbours".

"This is out to the blue, and as I've said, this has escalated out of a minor neighbourhood dispute," he said.

"It's just very hard to fathom how this has all unfolded," he said.

The firearms used in the shooting were registered and were recently inspected by the police.

"Victoria police found [the firearms] to be compliant ... and there is no history of domestic violence or violence in regards to these people."

The arrested man's wife was present at the time, and was helping police with their inquiries. Police are also speaking to "a number of other witnesses with various connections".

The editor of the Wedderburn Historical Engine and Machinery Society's newsletter, Geoff Maxwell, said Peter Lockhart was a "good member and a good worker".

"He joined the engine club after he retired, and has been a good member and a good worker," Mr Maxwell said.

"He's lived here all his life and I've been here for 50 years ... so I've known him for a while."

Mr Maxwell said Greg Holmes lived "across the road from Peter and Mary".

Locals in the main street, still waiting for confirmation of those involved, spoke of their shock on Thursday morning.

"Until we know which family, who we can step in to support, it's hard to know how to feel," Jenni, a shop owner said,

"I know what it was like when we lost a family of three kids [in a house fire some years ago], I know what we've been through. It's a country town, country people. We'll all step in."

Weddernburn RSL club president Bob McKenzie paid tribute to Mr Holmes, who served in Iraq as part of Operation Desert Storm.

"He was a good member, he will be sadly missed," he said.

Mr McKenzie said Mr Holmes donated his uniform to the club and it's now hanging on the clubroom walls.

Wedderburn mayor Gavan Holt said the "older deceased man was a fourth-generation farmer in the region".

"His wife was his second, and the younger deceased male was the woman's son, and the farmer's stepson," Cr Holt said.

He said the shooting had shocked the town of about 1000, and that it was "unbelievable what people do in a rage".

"A triple-murder in a community like this is just shocking," Cr Holt told Fairfax Media.

"We've got three people shot over a minor matter in a little country town - it's just shocking."

The minor dispute was related to farming practices, the mayor said.

"As I understand it, the man in custody had some minor neighbourly issues, which he and his neighbours did not agree on some time ago."

Cr Holt said he knew both the suspect and the deceased well, and that the suspect's sons had previously worked on his farm.

"All you can do is respect and support the family and friends of those involved," he said.

Counselling will be provided to anyone who needs it, Cr Holt said.

It is believed the man questioned by police has been in the town for at least two decades.

- with Tammy Mills and Bendigo Advertister