"We are talking about a big city, a widely spread city, to have the guy arrested either within 20 minutes or 35 minutes, I think is extraordinary," Nash said.
Nash also revealed more details around the man's arrest.
"These two guys pull this guy out but at the same time he was yelling, 'I've got a bomb' and shooting at the same time, so we overuse the word hero but not in this case."
When asked if the officers would be receiving bravery awards, Nash said he could not "pre empt anything" but there "aren't too many more acts of bravery higher than that".
"I'm very, very proud to be their Minister. I just think they have stood up when they needed to. I'm very proud of them."
The timeline of events for Friday's attacks which killed 50 people and wounded another 50 was about 40 minutes.
The accused gunman was arrested by two officers on Brougham St, following the shootings at both the Deans Ave and Linwood mosques.
The two officers, who had just come from a training session, rammed his car off the road in order to stop him.
Bush said this was "absolutely an international investigation".
It involved New Zealand police, the FBI, Australian police, and Five Eyes partners.
"To build a comprehensive picture of this person we will put before the court."
Bush confirmed there was just one attacker.
"A focus [of the investigation] is to figure out if anyone else was supporting him in any way. We are still conducting that part of the investigation."
They were not looking at anyone specifically.
At the accused gunman's next court appearance, at the High Court on April 5, there would "undoubtedly be more charges", Bush said.
"We are working towards, as you can imagine, a considerable number of the most serious charges."
Regarding the other people charged, Bush said was a lone man who appeared at one of the cordons with a firearm, and the others were a couple – a man and a woman.
The woman had been released while the man had been charged with a firearms offence.
"We do not believe they are related to the attacker in any way," Bush said.
Police had now formally identified 21 victims and their bodies would be released to their families.
"By end of Wednesday we should have identified all of the victims, some may take a little longer."
Bush said there were 120 people involved in the process, involving forensic experts from overseas, with the focus of "reuniting victims with loved ones".
While for police the number one priority was victims and families, on behalf of the Chief Coroner it was to ensure absolute accuracy in the identification process.
The other responsibility was prosecution.
"We must prove the cause of death to the satisfaction of coroner and judge. You cannot convict for murder without that cause of death."
Meanwhile, police have formally released the first five names of those killed at the Masjid Al Noor Mosque shootings.
They are:
• Haji Mohemmed Daoud Nabi (male)
• Mohsen Mohammed Al Harbi (male)
• Kamel Moh'd Kamal Kamel Darwish (male, from Jordan)
• Junaid Ismail (male)
• Mucaad Ibrahim (male)
