A couple viciously murdered in their Melbourne home were friendly, normal people who kept to themselves, a neighbour says.

The bodies of Robert Adamson, 65, and his wife Cheryl, 60, were discovered in the back of their Murrumbeena home of 40 years on Wednesday afternoon.

Police say both were brutally assaulted with a knife or possibly a blunt weapon.

Neighbour Ted Fentiman has known the couple for 40 years.

“(They were) very friendly, they’d certainly help you,” he told AAP.

“They were normal, next-door-neighbour types.

“We didn’t spend a lot of time in each other’s pockets. They kept to themselves.”

He said the couple would regularly spend Christmas with other neighbours in the quiet, conservative cul de sac where they lived.

“In years gone by, we got into the routine of having a street Christmas get-together.”

Mr Adamson was an accountant while his wife was the senior teacher librarian at Melbourne Grammar School’s primary school Grimwade House.

Melbourne Grammar School headmaster Roy Kelley said Ms Adamson was a dearly-loved staff member.

“Cheryl was a highly regarded member of the Grimwade House team, loved and respected by her students, their parents and her colleagues,” he said in a statement.

“Her loss will be deeply felt.”

The school is offering counselling services to staff and students.

Victoria Police Chief Commissioner Ken Lay said homicide detectives are still trying to determine what happened.

“We are treating it as a double homicide and working through a number of avenues of inquiry,” Mr Lay told Fairfax Radio on Thursday.

“Hopefully we get some better visibility on that over the next day or so.”

Detective Senior Sergeant Steve McIntyre said the couple were viciously assaulted.

“It is quite a brutal scene,” he told reporters on Wednesday.

“We don’t know what is behind these two deaths.”

The murders have shocked the neighbourhood.

“It sort of stuns you,” Mr Fentiman told Fairfax Radio.

“A normal suburban, quiet neighbourhood one day and the next day it’s a crime scene.”