Joel Cauchi was experiencing psychotic symptoms when he armed himself with a 30cm knife and rampaged through Bondi Junction Westfield on April 13, 2024.
Six people were killed and 10 others, including a nine-month-old girl, were injured before the 40-year-old was shot dead by police.
NSW Ambulance responded to up to 4000 calls for assistance on the day of the fatal stabbing, an inquest has been told.
Senior paramedic Brett Armitage said he had listened to some of the "quite horrific" calls and thanked the call centres for doing a "remarkable job" as the first point of contact.
Suspicions that there was a second assailant at the "chaotic" scene led to Mr Armitage, a NSW Ambulance assistant commissioner, declaring the scene as a "hot zone".
The declaration prevented the entry of paramedic crews from outside and required paramedics inside to withdraw.
The declaration, 52 minutes after Cauchi was shot dead, required paramedics inside to withdraw from the centre and barred other crews from entering.
At that time, police knew they were dealing with a single assailant but had not informed NSW Ambulance, the inquest into the attack has been told.
Mr Armitage was quizzed on Wednesday on a statement from a senior police officer at the scene who said he had been asked by a senior paramedic if the scene was still a "hot zone".
The police officer responded it was "still an active crime scene" and was asked to explain why paramedics were still inside.
"If any of my paramedics get hurt or stabbed, it's on your head," the paramedic allegedly said.
Mr Armitage "categorically" denied making the comment but stood by his decision to withdraw the paramedics from the centre.
The scene was never downgraded from a "hot zone", which Mr Armitage admitted should have occurred after 5pm when he knew there was not a second attacker.
Critical care paramedic Christopher Wilkinson said "confusion" at the scene meant paramedics were prevented from entering the shopping centre before the "hot zone" declaration.
"I stood there with my boots on the ground quite frustrated that people may well be dying upstairs and no one is doing anything medically for them," the four-decade veteran paramedic said.
"It's not good enough."
All injured people had been treated and removed from the building by 4.30pm and the declaration had no impact on the clinical outcomes of victims, the inquest was told.
The first of Cauchi's victims, Dawn Singleton, asked bystanders to call an ambulance after she was stabbed.
Police arrived within six minutes and commenced CPR, with paramedics arriving another 12 minutes later noting she had died.
"There is an expectation that if you ring an ambulance, it will come," Mr Wilkinson said.
The effectiveness of inter-agency communication during mass casualty events is a key topic being canvassed at the inquest.
Mr Wilkinson, who has been trained in dealing with mass-casualty events, said lives were lost when emergency services did not communicate effectively.
He emphasised the "need to change the way we do things" but commended paramedics who responded to the tragedy.
"At Bondi, it made me very proud to be a paramedic," Mr Wilkinson said.
Ms Singleton, 25, Faraz Tahir, 30, Ashlee Good, 38, Jade Young, 47, Pikria Darchia, 55, and Yixuan Cheng, 27, were killed in the attack.
Cauchi, who stabbed his first seven victims within 30 seconds, had been diagnosed with schizophrenia as a teen and had been successfully treated until 2019 when he stopped his medication.
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