The commotion was also heard by a nearby ambulance officer beginning his shift, who rushed to the property to help.
Police shot dead the deer, which the family had owned for about two years, to protect paramedics trying to save the couple.
Mr McDonald, a farmer who did odd jobs at other properties in the area, died from his injuries at the scene shortly after the attack.
Ambulance Victoria said Ms McDonald was treated for upper body and leg injuries and flown to The Alfred hospital with life-threatening injuries.
Ms McDonald is a passionate gardener and has owned the Linga-A-While nursery in Wangaratta for three years, after taking over the 20-year-old business from her father.
She also works at Ineeta Cafe and had recently penned columns for the local paper Wangaratta Chronicle.
Ms McDonald, 45, had concerns about keeping the deer at the enclosure.
“I know Mandi was always a little bit hesitant with going near it,” a friend, who did not want to be named, told The Age.
Moyhu is a small, close-knit community and the town has been rallying around the family, who also had sheep on their small property.
Autumn is mating, or rutting, season for many species of deer, and is a particularly dangerous time to be around the wild animals.
“An animal that would be otherwise docile for 10 months in the year, is an animal you really don’t want to be around for two months,” said Barry Howlett from the Australian Deer Association.
Stags grow sharp antlers and, filled with testosterone, aggressively fight with each other and other animals, including cows.
Mr Howlett said that deer can become a danger to humans in domesticated scenarios.
“It’s not an everyday occurrence, but it’s not unheard of for deer to kill people in that situation,” he said.
“Deer stop eating, they shed a huge percentage of their body weight. They stop doing everything except for finding a female partner and become extremely aggressive,” Mr Howlett said.
There are as many as a million feral deer in Victoria, according to a 2017 state government report, with some species increasingly found in urban areas.
The number of deer – and their spread – is rapidly increasing in Victoria, including near cities. Deer have been reported in backyards and schools, and rutting deer have been seen harassing cattle.
Victoria’s deer population is primarily made up of four species: sambar, fallow, red and hog deer. Mr Howlett said fallow and red deer become particularly aggressive during the mating season.
He added that Australia’s deer farming industry, where valuable velvet is extracted from antlers, has “declined greatly over the last 20 to 30 years”.
“There’s still some people with serious velveting operations, and there’s hobbyists who keep deer in a pen because they’re an exotic novelty.”
About 100,000 are shot every year in a hunting trade worth about $140 million to the state. The Parks Department has proposed funding a bigger hunt to control the growing number of feral deer throughout Victoria.
with AAP, Border Mail, Nine News
Michael is a reporter for The Age.
Liam is The Age and Sydney Morning Herald’s science reporter
Rachel is a breaking news reporter for The Age.