Fifty people were killed after a gunman opened fire at two mosques in Christchurch on March 15. At least 40 others were injured.
A man faces 50 charges of murder and 39 counts of attempted murder. He is yet to enter any plea and is in an Auckland jail. He will next reappear in court in June.
“I have said previously that the public should have as much information as possible about our response, and the timeline we have released today provides further clarity," Mr Bush said.
"I want to emphasise we are still in an investigation phase and now a prosecutorial stage."
"The information released today is currently the best information I have to date and what I can release without compromising the criminal investigation or the trial," Mr Bush said.
The timeline provided begins at 13.40 on March 15.
An email which has the manifesto as an attachment is received by a range of people including Parliamentary Services. At 13.40.44 Parliamentary Services calls South Comms.
"I would like to thank Parliamentary Services security staff for their swift action in contacting police."
The call from Parliamentary Services lasts for 12 minutes.
"We now know that while police was talking to Parliamentary Services the attack at Al Noor Mosque was already underway, having begun 44 seconds prior to Parliamentary Services calling."
By 13.43 all available units are en-route to Al Noor Mosque.
Armed Offenders Squad members are the first to arrive near the scene at 13.46.58.
They exit their vehicle, start approaching the mosque and one member stops to assist a critically wounded victim.
At this point the alleged offender is leaving the area, and his vehicle is obscured from the view of these AOS members by a bus.
At this time there is no vehicle description, no information an offender has left the mosque, or how many shooters there are.
First responders arrive at the Al Noor Mosque at approximately 13.51.
It takes the alleged offender 6 minutes to get to Linwood Mosque and he is there for three minutes, leaving at 13.55.
At 13.56.09 police receives information that shots have been fired at the Christchurch Emergency Department.
It later transpired that no shots had been fired at the hospital.
Sixteen seconds later at 13.56.25 a member of the public flags down a police car to advise shots have been fired in Linwood.
At 13.57 the vehicle is seen by a police unit on Brougham Street and a pursuit is initiated.
The vehicle is stopped at 13.59 and the offender is apprehended.
Police arrive at Linwood Mosque
At 13.59 police also arrive at the Linwood Mosque.
There are 18 minutes from the time of the first call to 111 to the apprehension of the offender.
"I reaffirm my previous comments that Police staff acted as quickly as humanly possible given the rapidly unfolding nature of the event, and the information available to us in that very brief period of time, " Mr Bush said.
"As part of normal operational practice we are debriefing our response.
"In order to provide absolute transparency this will be done by an independent team, including a Queen’s Counsel.
"The debrief is an important process to ensure any lessons are learnt, and used to inform future operational responses.
"I remain incredibly proud of the staff who responded on March 15 and I continue to receive praise and admiration from people both here and overseas for the actions of staff both on the day and in the weeks following," Mr Bush said.
International presence
"I am also very grateful for the assistance provided on the day by several of our international colleagues who were here for a specialist training course.
"Police Officers from Queensland, New South Wales, Victoria, Western Australia and Hong Kong, as well as New Zealand Defence Force personnel, responded with our staff and rendered initial first aid to victims at the Linwood mosque.
"Their specialist skills have been credited with saving lives and we were fortunate to have them on the ground with us."
