The police shooting of a man in Broome on Tuesday has put a spotlight on the rules that govern police using their guns.

The incident — involving a man in his 60s who was allegedly wielding a knife — is still under investigation.

So when can officers draw their guns?

WA Police Commander Lawrence Panaia said officers were trained to use a "force option" commensurate with the threat.

"They're trained on a tactical options model, to assess the situation and then determine which force option is most appropriate," he said.

"Police shootings are very, very rare — I think the last one was over a year ago.

"It's not something that we take very lightly of course, and it's something that's at the very serious end of what we do."

The Major Crime Squad investigate all shootings, with oversight from Internal Affairs.

The officers themselves receive counselling through the WA Police health and welfare branch.

The union is also involved, assisting officers involved in shootings with welfare and legal issues.

What's changed in the way police shootings are handled?

The big change in police inquiries into shooting incidents in WA came after the fatal shooting of Brendan John Lindsey in the Perth suburb of Carlisle in November, 2014.

Brendan John Lindsay was shot dead by police in 2014. ( ABC News: Graeme Powell )

Lindsey had taken a deli worker hostage and threatened to kill her with a knife.

He was shot dead after he started stabbing the woman.

Four officers involved were arrested and held by Internal Affairs for up to 13 hours. None were charged and it was found Internal Affairs had not acted unlawfully or maliciously.

But a review led to a streamlining of investigations, with the handing over of primary responsibility to the Major Crime Squad.

Major Crime carried out the initial investigation into the shooting of Daniel Ashley in Mosman Park in June 2015.

He had taken hostages and refused demands to drop his weapon, which turned out to be a replica.

Ashley, who was left a paraplegic, was later sentenced to six years in prison.

Police actions were deemed to be lawful.

'Your life does flash before your eyes'

Union president George Tilbury said the safety and welfare of officers was a paramount consideration.

"It's a terrible situation for anyone to go through, particularly the police officer, when they have to make a decision to use lethal force, or force that could end up being lethal," he said.

Using lethal force is often a decision made in a split second, the union says. ( ABC News: Anthony Stewart )

Police training on when to use force includes the consideration of alternatives, and minimum force is generally recommended.

But Sergeant Tilbury said there were times when decisions had to be made quickly.

"That's a situation where police officers have to make split second decisions," he said.

"Particularly with sharp edged weapons that can kill you, that can cause you serious harm — and police first and foremost need to look after themselves.

"But also on your mind is that pepper spray and tasers don't always work, so you have to consider that as well.

"When you're in that situation you have to stop that threat to either preserve your own life, your partner's or any other innocent party.