The mistake meant an Armed Offenders Squad (AOS) member thought he had "stuffed up" and left an offender free to shoot more people at the mosque on Deans Avenue on 15 March, 2019.
The inquest into the murder of 51 worshippers at the Al Noor Mosque and Linwood Islamic Centre has heard a senior policeman did not realise the terrorist's Facebook stream of the attack was delayed when he transmitted a description of the gunman over the radio.
Detective Superintendent Darryl Sweeney described seeing the terrorist get out of his car, walk into the mosque and fire his gun.
"I thought I had stuffed up and left an offender there and he was killing people."
When he returned to the mosque, he realised that it was a mistake and his time had been wasted.
The AOS member also told the court none of his training could have prepared him for the scene he came across inside the mosque's main prayer room.
Bodies laying on the ground outside the mosque made him realise they would be dealing with a mass casualty event, but nothing prepared him for the number of bodies piled up in the room, and the smell, he said.
He was "overwhelmed" by the scene and called multiple times for ambulance staff to come and help injured victims inside the mosque.
An initial clearance of the building had been completed, and the AOS member said he was confident ambulance staff could enter by 1.59pm.
A few minutes later, he called for ambulance staff to "come forward" but still, none came.
He told the court he understood the risk involved, as areas surrounding the mosque had not been thoroughly checked, so ambulance staff may have been hesitant to come into the mosque.
He said he completed a quick triage of victims, asking anyone who could walk to get out of the mosque.
Assessing two injured worshippers, he quickly realised the medical kit his team had with them was not going to be enough - and people needed to get to hospital straight away.
The AOS member was asked by Nikki Pender, lawyer for victims and their families, if there was anything that could have been done to make the police response quicker.
He told her the radio in the room he was in at the time had been turned down for a meeting earlier in the day, and never turned back up.
Had the volume up, they may have heard the 111 calls three minutes prior to the page he received. This meant he and another team member could have got to the mosque three minutes earlier than they did - but the outcome of that was unknown.
"We could have stopped the offender, or we could be dead."
The inquest will examine the following 10 issues over six weeks:
- the events of 15 March 2019 from the commencement of the attack until the terrorist's formal interview by police
- the response times and entry processes of police and ambulance officers at each mosque
- the triage and medical response at each mosque
- the steps that were taken to apprehend the offender
- the role of, and processes undertaken by, Christchurch Hospital in responding to the attack
- coordination between emergency services and first responders
- whether the terrorist had any direct assistance from any other person on 15 March 2019
- if raised by immediate family, and to the extent it can be ascertained, the final movements and time of death for each of the deceased
- the cause of death for each of the victims and whether any deaths could have been avoided
- whether Al Noor Mosque emergency exit door in the southeast corner of the main prayer room failed to function during the attack and, if so, why?
The inquest continues.
