The house is across the road from the reserve where the attack happened.

Mr Messo's parents had responded to an advertisement on Gumtree, saying they were looking for a room for their son.

Once he had moved in, Ms Messo would come to check on her son and spend time with him three or four times a week. She also paid the rent.

"[My parents] were saying she was a very nice, innocent, sweet lady," Mr Panagoda said. "From what I gather ... she was very reserved, quiet, just a loving mother at the end of the day."

Mr Panagoda said his parents told him that Mr Messo, who was unemployed, would often say that he loved his mother.

"He didn't seem out of the ordinary," he said.

"He just sort of seemed reserved and to himself. The only time I saw him was last week, just outside, yelling on the phone.

"He was just really quiet, he had told them he is vegetarian and doesn't like partying and kept to himself. But they noticed, Dad had said on a phone call with him he would flip from one calm moment to aggressive, he could sense that in his voice."

Mr Panagoda was on a walk on Thursday afternoon when he saw the incident unfold outside his home.

"I was walking back to get home and was in front of my house and heard a car speeding behind me," he said.

"Then a marked cop car with lights on and no siren came up to the intersection and the passenger cop already had his door open. He jumped out.

"I didn't know what was happening until I got to the corner and that's when I saw a male sitting down on the field towards the trees. He was facing the cops and acting really aggressively, erratic and screaming. I couldn't make out what he was saying.

"Then the cops approached him and the guy's hands were going up and down, up and down with a weapon, maybe a club or a brown pole, in his hand.

"Police were screaming at him, yelling commands at him and he wasn't responding."

Mr Panagoda said police then fired a shot but there "was no reaction from the guy".

"There was no fear in him," he said. "He stood up again, he went towards the two officers ... that's when they fired the second and third round. Then the guy dropped to the ground ... I saw blood all over his shirt.

Bystanders tried to help the severely injured woman as dozens of police cars swarmed the area.

On Thursday night, Assistant Commissioner Luke Cornelius said the junior officers at the scene were "terribly shaken up" by the shooting.

Without naming Mr Messo, Mr Cornelius said the officers had told him to stop, but he refused.

"Our members then drew a firearm and discharged their firearm and that resulted in the death of the male assailant," he said.

"No member goes to work expecting to have to take the life of another person and that is very difficult and thankfully a decision that does not happen too often.

"But when a police officer does make that decision, of course, it has a terrible impact on that member and also of course generate significant concern for the wider community."

Mr Cornelius said police had sought to help Mr Messo in the past.

"We've had recent contact with him, but there was nothing in that recent contact with him that indicated to us that the events of today might have occurred," he said.

Police are appealing to the "numerous" eye witnesses to the attack to come forward, while the shooting will be investigated by professional standards command.

The State Coroner will now investigate the death after visiting the scene late on Thursday.

"Victorian State Coroner, Judge John Cain attended the site of the police shooting in Gladstone Park
last night, to commence a coronial investigation into the fatal incident," a spokeswoman said. "His Honour has directed that Victoria Police compile a coronial brief of evidence

"His Honour is also empowered under the Act to make recommendations to address systemic issues
to prevent similar incidents in the future.

"As the investigation is ongoing, no further comment can be made at this time."

Anyone with information should contact Crime Stoppers on 1800 333 000.

For help in a crisis call 000. If you or anyone you know needs support, you can contact the National Sexual Assault, Domestic and Family Violence Counselling Service on 1800RESPECT (1800 737 732), Lifeline 131 114, or Beyond Blue 1300 224 636.