KENYA'S shopping mall massacre shook the world. Yet all it took was four terrorists with guns. Now, investigators say they all escaped.

It's a story of chaos, confusion - and corruption.

The New York Police Department has conducted its own in-depth analysis of the September attack which killed more than 60 at the Westgate Shopping Mall in Nairobi. It was an exercise designed to familiarise the often-targeted city's law enforcers with what to expect.

Their discoveries have debunked much of what Kenyan authorities claim, and painted a frightening picture of the power of a few angry men with guns.

And they doubt the terrorists died in the collapsing building.

"As a cop, I'm very sceptical of claims until I see proof," Lt. Detective Commander Kevin Yorke, who oversaw the report, said. He added that there is "a lot of doubt in my mind it is true."

Detective Yorke said it was only now a real picture was emerging from 'the fog of war'.

But the most startling component of the report is the dangerous incompetence shown by Kenya's military and police reaction.

Here's what the NYPD found.

News_Rich_Media: Repeated gunfire can be heard as supermarket shoppers take cover at the Westgate Mall in Kenya. Courtesy CCTV Africa

Tiny attack force

Kenyan authorities have repeatedly claimed that up to 15 heavily armed attackers from the al-Qaeda affiliated al-Shabaab terror group were involved in the operation which overwhelmed the African nation's police and defence forces for three days. Some were supposed to be foreign nationals.

New York Police Commissioner Ray Kelly told media yesterday his investigators did not know "with certainty" how many people were involved, "but we believe there were only four shooters."

Their reconstruction of the attack suggests the four men acted in teams of two, coordinating their movements via mobile phone.

News_Image_File: Light attack ... The Kenyan mall attackers are believed to have been very lightly armed. A more determined and early police response may have prevented the high number of casualties. AP

Lightly armed

They were supposed to have been wielding heavy machineguns and explosives. But the NYPD says a review of video footage and ballistics evidence shows they were carrying only "light" weapons such as AK-47 rifles and grenades.

Three grenades were used upon their entrance to the mall, after which the terrorists used single-shots to target fleeing shoppers.

While carrying hundreds of rounds of ammunition in magazines strapped to their bodies, the NYPD says the attackers were not wearing any form of body armour or carrying handguns.

There were no heavy explosions. Smoke screens had not been created by setting mattresses and other materials on fire.

Instead, the NYPD says all of the heavy damage to the shopping mall's structure had been caused by antitank missiles being fired into the building by Kenyan military.

News_Image_File: Confused response ... Kenyan police and military forces appear not to have been communicating. As a result, a team of unmarked and plain-clothed police officers appears to have been attacked by Kenyan soldiers. AFP

'Friendly fire'

Initially, Kenyan authorities believed they were responding to an armed holdup. A tactical response team did not arrive at the Mall until some 90 minutes after the initial attack.

From this point, confusion reigned.

Police - wearing no identification or markings - entered the complex, fully armed.

They were quickly fired upon by Kenyan soldiers who had also been summoned to the scene. Among the dead was the police tactical response team's commander.

It was this incident that may have produced the stories of "heavily armed, body-armour-wearing" terrorists.

News_Image_File: Light and mobile ... The terrorists are believed to have not taken any hostages, preferring to test - then shoot - their victims. (AP /Jonathan Kalan)

No hostages

The presence of hostages was always used as an excuse for the slow military response to the shopping-mall raid. Now, the NYPD says it doubts there were any.

Instead, the report says the terrorists sought to kill as many as they could.

RELATED: Video shows horror inside Westgate Mall

Only those who were able to recite Muslim prayers - and in once instance name the Prophet Mohammed's mother - were allowed to go free.

The idea that there may have been hostages is thought to have arisen because by so many shoppers were "playing dead" and hiding.

News_Image_File: Off the scene ... Wanted terrorist and British citizen Samantha Lewthwaite was not a part of the Westgate Mall attack force, say the NYPD.

White Widow 'distraction'.

A NYPD review of witness accounts and CCTV footage indicates no women were involved, the report says.

RELATED: Blood-stirring ode and weight loss worries: Lewthwaite's secret files

Media speculation - apparently encouraged by statements from Kenyan officials - named British citizen and al-Shabaab terrorist Samantha Lewthwaite as one of the attack team storming the shopping complex.

News_Image_File: After the horse had bolted ... Kenyan soldiers clear the shopping complex on September 24 - three days after the terrorists appear to have fled. AFP / CARL DE SOUZA

Early escape

The gunbattle to clear the mall lasted three days. But there is no evidence the terrorists were there beyond the first 12 hours.

NYPD investigations indicate at least one of the attackers was wounded in the leg. But the fighters systematically destroyed CCTV cameras in order to cover their movements.

And their actual attack only lasted six hours. After this, the NYPD report says the terrorists hid in a storeroom. Here, they prayed and tended to their wounded comrade.

RELATED: Security 'looted shops' during Westgate siege

There is no evidence any attacker remained in the mall after 12:15am on September 22, the NYPD says.

Despite this, the siege lasted another two days.

During this time CCTV footage captured members of the Kenyan military looting the high-end shopping complex under the cover of the crisis.

News_Module: NND Nairobi Terror image