Victoria police have said officers shot dead a man after witnessing him carry out a “frenzied attack” that left an older woman in critical condition in the north-west Melbourne suburb of Gladstone Park.

Police were called to John Coutts Reserve in Gladstone Park at around 3:30 pm on Thursday after receiving a number of reports of a man assaulting a woman.

Six minutes after the first call, officers showed up at the scene and allegedly discovered a man, who is said to be in his 30s, “seriously assaulting an older female” in what assistant commissioner Luke Cornelius called a “frenzied attack”.

Cornelius continued to reveal that police fired shots within 30 seconds of arriving at the scene after the man ignored authorities’ repeated requests to stop assaulting the woman.

The woman is currently in critical condition at the Royal Melbourne Hospital. She has not been identified due to the extent of her injuries, but according to Cornelius, police believe the man and woman were known to each other.

“It was not a random attack,” he said.

Cornelius said the man was known to police but had no criminal record, and that recent contact with him did not indicate “the events of today might have occurred”.

He said the officers who shot the man were “junior members early in their career”.

“They found themselves having to make one of the worst possible decisions that any member has to make in their career, so my heart goes out to them,” Cornelius said.

“We’re going to wrap our arms around those members and assure them of our support, assure them of our backing.

“They’ve done the best to stop a terrible attack from continuing, and tragically, despite their best efforts, it has resulted in the death of a male, who we believe was the assailant, and also very, very serious injuries to the female, who was the subject of that frenzied attack.”

The assistant commissioner said policing was a very tough profession that required members to make difficult decisions in high pressure scenarios.

“Our members are called upon to act decisively. Our members are called upon to take action. It’s apparent to me based on what I’ve been briefed about this afternoon that our members have done exactly what we expect of them.”

The police said homicide squad detectives would investigate the incident, overseen by professional standards command, according to protocols when weapons were discharged.