In the US, geeks who have spent thousands of hours on computer games have been employed as military drone pilots and, closer to home, kids who have honed their driving skills on racing programs up the thrill by stealing real cars to take on police.

One 13-year-old in the northern suburbs who could hardly see over the dashboard told police after the inevitable high-speed crash: "You would never have caught me if I hadn't stolen a manual."

Would be terrorists are recruited via online sites and trained on the Dark Web. Local gang leaders watch videos of street fights to identify new muscle and now police are turning to international scenario training in a change in tactics in dealing with armed offenders.

Police firearms training used to consist of a few shots at the range followed by a few pots at the pub (an examination of the bullet holes in the roof and walls of one police facility indicated the order may have occasionally been reversed).

But shooting at a range is nothing like the real thing. There is no adrenalin, no doubts and no fear. And the targets can't fight back.

And so police have built a $1.8 million simulator to replicate up to 100 scenarios from an aggressive street confrontation, where police will try to negotiate a peaceful outcome, to a shootout with a possible mass killer.

The aim is to make it as realistic as a commercial flight simulator, which can produce just about any emergency that could occur in the air (other than running out of pinot noir in business class).

This is not a computer screen but a life-size, 300-degree, five-screen darkened room where the police are armed with replica firearms linked to the software program.

On the screens can be an armed, drug-affected suspect, a man threatening his partner, or multiple armed offenders who have already opened fire. Police can respond by negotiating, confronting, using capsicum spray or deadly force.

Out of sight a supervisor has a series of computer options so the on-screen characters can react to the real police's responses.

When Naked City watched one scenario we failed to see that a drug offender was armed with a syringe until she brandished it as a weapon. In a mass school shooting played out on the five screens we would almost certainly have shot a fleeing student who for a split second was mistaken for a gunman.

"The decisions police make in microseconds may ultimately have to be explained at the Coroner's Court," says Assistant Commissioner Kevin Casey.

Philosophy shift

This is more than a new training tool - it represents a major shift in police philosophy and a direct response to the growing local terrorism threat.

As a result of a spate of police shootings in the 1980s, Victoria Police underwent a massive retraining program called Project Beacon, in which the safety of police, the public and suspects was given the highest priority.

The old way of rushing in (a method described by then coroner Hal Hallenstein as a culture of bravery) was replaced by cordon and contain. The thinking, particular in sieges, was the longer the incident is contained the more likely it is to resolve peacefully.

For about 25 years the first police on the scene cleared people away, created a cordon and waited for the experts, hostage negotiators, snipers, and specialist forced entry officers, to arrive.

The experts would be equipped with psychological profiles, distraction bombs, tear gas and some tricks we aren't going to talk about.

But Sydney's 2014 Lindt cafe siege has changed the rules of engagement and police nationwide have accepted that cordon and contain plays into the hands of terrorists. While it is still a valuable tactic in many situations, it is no longer a one-size-fits all solution.

"It's the reality of the world today and we need to prepare ourselves," Superintendent (Operational Safety Division) Peter Seiz says. "Previously, it was about cordon and contain and communicate, peaceful resolution. World events have taken us out of that area, and have put us in a place where members, depending on the circumstances, might have to engage."

Shoot to kill

So now there are two new police phrases that are clinical but deadly: "Active Armed Offender" and "Casualty Reduction."

First there is an active shooter - the sort of incident repeated with sickening regularity in the US where a gunman walks into a school, college, cinema, shopping centre or workplace with the sole intention of killing as many people as possible.

This means the first police on the scene - likely to be relatively inexperienced patrol officers - will be expected to take immediate action, options that include killing armed offenders to stop them shooting.

"Our job is to protect life first and foremost and we might need to get into or resolve a situation where a decision might have to be taken to take an offender's life." says Seiz.

In Australia often the most vile mass killers have been taken alive, such as Julian Knight who in 1987 murdered seven unarmed people and injured a further 19 in Hoddle Street before immediately surrendering when he faced armed police. For the deluded Knight, toughness was all about holding a gun - not looking down the barrel of one. Or Martin Bryant, who in 1996 killed 35 people and wounded another 23 at Port Arthur.

But it is not just guns these days, as events as close as Bourke Street and as distant as France show that anyone with a set of car keys can become a mass killer.

When you sign up to join the Special Operations Group or one of several sharp-end police units you know what comes with the territory, but under active offender training we will be asking regular cops to be heroes.

"It's the reality of the world today and we need to prepare ourselves," says Seiz.

Front line crucial

This is not the first time police have used US-style training videos. After a series of random attacks on police (burglar Pavel "Mad Max" Marinof shot four in 1986, the Russell Street Bombing in the same year and the Walsh Street murder of two police in 1988), senior police believed we were heading to the US where criminals carried guns and any interaction with the public could turn fatal.

And so police used a video called Your Move Sergeant where an action sequence would be stopped and the trainees asked what they would do next. The change in tactics coincided with an influx of recruits to honour a government promise of a boost in police numbers.

The consequence was more inexperienced police on patrol and an increase in the number of police shootings.

Today the government has promised an increase of 3000 (with resignations and retirements this really means more than 4000 recruits), which means we will have an inexperienced front line at a time when more criminals are carrying guns, ice-related violence is at a record high and the risk of lone-wolf terror attacks is ever present.

Which is why, says Assistant Commissioner Casey, training must be as realistic as possible to prepare young police for the real thing. "Police who graduate on the Friday may be on the [patrol] van on Monday and will have to make crucial decisions on the spot."

Young police such as Adam McKenzie, who was on his first night shift just three weeks after graduating in 2008 when he shot dead a gunman who had wounded another officer. his month McKenzie was awarded the prestigious Valour Award.

As well as virtual reality training, police have built an indoor village to practise responses to armed robberies, building sieges and random shootings.

International experience shows that terror groups can drag out sieges and pretend to negotiate to "milk" maximum publicity for their twisted causes. In Europe, terror groups will try to lure counter-terror police into a shootout.

Senior police say that in a terror-related hostage siege, direct action - moving in with an element of surprise - is safer than waiting, only to be forced into emergency action after shots are fired, as was the case at the Lindt cafe.

This means that in Victoria, general-duties police trained in active-shooter tactics may be asked to take immediate action rather than wait for heavily armed specialists. "In certain circumstances it is all about casualty reduction rather than seeking a peaceful resolution because negotiation doesn't work with terrorists," according to one senior policeman.

In such cases the elimination of the threat is the main priority. Police will run past the wounded to find the gunmen. Options will be to contain the threat by creating a barrier to more victims, ordering the offenders to surrender or killing them if necessary.

Assistant Commissioner Casey says police will respond to the actions of the offenders. "We will use proportionate force to stop the threat."