Four officers involved in the fatal shooting of a Melbourne father after he killed his own son did not have access to stun guns.
The officers were confronted by the knife-wielding 54-year-old man at the Tyabb cricket oval on Wednesday evening and tried to subdue him with capsicum foam, police say.
Victoria Police Commander Doug Fryer said officers also tried to talk him down after he brutally killed his 11-year-old son at the Mornington Peninsula sporting grounds.
"I can't go into exactly what happened, but I can say any attempts at talking him down were unsuccessful and they discharged a firearm, hitting him once in the chest," he said.
The man later died in hospital.
Victoria's rollout of stun guns is continuing, but the four officers at the scene on Wednesday did not have Taser training or access to the electro-shock weapons, said Police Association secretary Greg Davies.
He noted that police used a Taser in Ballarat to stop an armed and enraged teenager on the same day as the fatal police shooting.
Officers in Tyabb did not have that option available.
"They were placed in a horrific situation," he said.
"What do people expect them to do? He's already killed his own son and there's potentially dozens of other children in the vicinity."
He said it appeared police had "no alternative" but to use lethal force - but he stressed that official judgments would need to be made by the coroner and within internal investigations.
Victoria delayed a rollout of Tasers for years before finally announcing a trial in March 2012.
Officers in Ballarat gained access to stun guns in May while police in Bendigo, Geelong and the Latrobe Valley also have the devices.
In Melbourne, only Special Operations Group officers and the Critical Incident Response Teams have Tasers.
The mother of 15-year-old Tyler Cassidy, Australia's youngest police shooting victim, said after his inquest that he would still be alive if police had been given Tasers back in 2008.
Many police officers believe Tasers can be a valuable way of resolving serious incidents and confrontations with irrational or drug-affected people.
But human rights advocates have lobbied strongly against stun guns, citing an Amnesty International report that linked Tasers to the deaths of hundreds of people.
A high-profile Canadian inquiry held after two dozen fatalities also found stun guns can lead to death.
US-based Taser International has consistently denied the devices can be lethal.
It's believed Victoria's roll-out of Tasers could take until the end of 2015 before it's completed.
