Police have confirmed it took them 18 minutes to make an arrest after first being called to shootings at two Christchurch mosques.

The shooting saw 50 people killed and a further 39 injured after the terror attacks at Al Noor Mosque and Linwood Mosque on March 15.

While reducing the country's threat level from high to medium, Police Commissioner Mike Bush said he wanted the public to have as much information as possible about their response to the two incidents.

However, given the matter was now before the court there were certain details that couldn't be released.

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"The investigation team continues to be focused on confirming certain details, particularly timings sourced from a number of electronic systems and devices with differing internal clocks.

"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."

The timeline kicks off at 13.40.

An email which has the manifesto as an attachment is then received by a range of people including Parliamentary Services.

At 13.40.44 Parliamentary Services calls South Comms, a call which will continue 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," Bush said.

One minute later, at 13.41, police received the first 111 call.

Police today released this map and timeline of the March 15 terror attacks in Christchurch. Image / NZ Police
Police today released this map and timeline of the March 15 terror attacks in Christchurch. Image / NZ Police

"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."

It was at this point the alleged offender was leaving the area, and his vehicle obscured from the view of AOS 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."

At 13.51, the first responders arrive at the Al Noor Mosque.

"It takes the alleged offender six 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. However, it later transpired that no shots had been fired at the hospital.

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 St and a pursuit begins.

The vehicle is stopped at 13.59 and the offender is apprehended.

At the same time, police arrive at the Linwood Mosque.

There are a total of 18 minutes from the time of the first call to 111 to an arrest being made.

"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.

"As part of normal operational practice we are debriefing our response."

That debriefing 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."

1.40pm Email is forwarded to the Security Team at Parliament. A 74-page manifesto is attached along with links to web pages where content can be downloaded

Police Communications

1.40:44pm

Parliament calls Police Communications. Caller scans the manifesto and relays information. Call lasts about 12 minutes.

1.41pm First 111 call from public.

1.42pm Comms report over radio a priority one firearms event of machine gun fire at mosque on Deans Ave.

1.46pm 12 firearms events have been received by Comms.

1.50pm A description of the offending vehicle and its registration are shared over the radio.

1.53pm Radio report a vehicle description matching the alleged offender's is sighted on BealeyAve heading towards Fitzgerald Ave.

1.57pm A call to Comms indicates shots are being fired around Linwood Ave and Hargood St.

Police Responders

1.43pm

Multiple units respond and indicate they are on their way to Deans Ave.

1.46pm Armed Offender Squad (AOS), responding to the firearms event, arrive at corner of Deans Ave and Riccarton Rd.

1.47pm AOS confirm over the radio they are making an approach on Deans Ave.

1.48pm One AOS member stops to administer first aid to a gunshot victim.

1.49pm Another AOS team leave the police station.

1.51pm Police first responders arrive at Al Noor Mosque.

1.54pm Police responders including an AOS member indicate they are on their way to BealeyAve.

1.56pm Report over police

1.56pm A local police unit in the area is flagged down by a member of the public reporting shots fired in Linwood.

1.57pm Police pursuit initiated along Brougham St with intersection of Waltham Road.

1.59pm Alleged offender apprehended near Strickland St.

1.59pm Police first responders arrive at Linwood Mosque.