Police say the gunman parked across the street from the Masjid Al Noor before the March 15 2019 attack.

Police say there is no evidence the man behind the Christchurch mosque attacks had been inside one of the mosques prior to the attack.

Last month, a 29-year-old Australian, made a shock guilty plea to 51 charges of murder, 40 charges of attempted murder and a charge of engaging in a terrorist act. A sentencing date is yet to be confirmed.

A summary of facts outlining exactly what happened that day, and the events leading up to it, is expected to be made public at the sentencing.

It has been suggested the shooter entered the Masjid An-nur (Al Noor) mosque prior to March 15.

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In a promotional video clip for a Newshub story to be aired on Sunday night, the An-Nur Imam Gamal Fouda is shown saying the shooter had previously prayed in the mosque and knew it "like his house". Fouda told Stuff the interview was from April last year.

GEORGE HEARD/STUFF Fifty-one people died as a result of the March 15, 2019 attack.

Fouda told Newshub a European man, who he believed to be the gunman, visited the mosque during Friday prayers at least three times prior to his attack. "He came and he prayed in the mosque."

He said in one of the visits the man wore Pakistani dress, which made him stand out.

​However, on Sunday afternoon Canterbury District Commander Superintendent John Price confirmed police had carried out an "extensive investigation" and there was no evidence to suggest the gunman entered the mosque or its grounds prior to the March 15 attack.

ALDEN WILLIAMS/STUFF In a television interview, Imam Gamal Fouda says the shooter had been inside the mosque before and knew it "like his house".

"After police extensively reviewed CCTV footage as part of the investigation, it was found he had parked across the street before March 15.

"Police also believe he viewed an online tour of the mosque."

While the matter remained before the court Price was unable to provide any further information.

Frank Films Frank Film and Stuff followed mosque shooting survivor Temel Atacocugu through his long recovery from physical and mental trauma.

NZ'S WORST MASS SHOOTING

It is known that on March 15 last year, the gunman drove from his Dunedin home to Christchurch with an arsenal of guns and ammunition he'd amassed since moving from Australia to New Zealand in 2017.

The white supremacist entered Masjid An-nur on Deans Ave as Friday prayers were beginning, about 1.40pm, and opened fire – killing and wounding dozens of people.

He then drove across town to the Linwood Mosque where he continued his shooting spree.

He was arrested a short time later after his car, a gold Subaru Outback, was rammed off the road by two police officers on Brougham St as he tried to make his way to a third target, thought to be a mosque in Ashburton, where he planned to carry out another attack.

When police searched the vehicle they found several guns and petrol bombs.

In total, 51 people were killed in the terrorist attack, the worst mass shooting by an individual in New Zealand history.

The gunman was the first person to be charged under NZ's Terrorism Suppression Act 2002.