It was just after three o'clock and the Westfield Bondi Junction shopping centre was teeming with people. Suddenly, screams filled the air: a man with a knife was on the rampage, stabbing women and even a nine-month-old baby. But while most people made for the exits or barricaded themselves in shops, a police officer raced to confront the attacker.   

Inspector Amy Scott was following her normal duties when reports of the incident came through. By the time she reached the mall, the knifeman - later identified as Joel Cauchi - had killed six people and wounded twelve others.

The armed policewoman tracked him to the fifth floor and shouted "Put it down!" Instead, he raised his knife; Scott shot him, and he fell to the ground. She then hurried to throw the knife clear and attempted to revive him - but Cauchi was already dead.

Australia's prime minister, Anthony Albanese, described Scott as a hero. "There is no doubt that she saved lives," he said. The incident, he added, was "a reminder that those people who wear uniform are people who rush to danger, not away from it."¹

Yet Scott was not the only person who showed enormous courage. Some of the shoppers knelt to help the wounded instead of seeking safety. One man, Damien Guerot, confronted Cauchi armed only with a pole to stop him reaching a children's play area.  

The word "hero" generally evokes a fearless warrior such as AchillesThe Greeks' greatest hero. The only vulnerable part of his body was his heel - hence the expression "an Achilles heel", meaning a weak spot.. But heroes can take unexpected forms. Roy Larner, who has criminal convictions for assault and possessing drugs, is a case in point.

In 2017, when three terrorists armed with 12-inch knives attacked people on London Bridge and in Borough Market, Larner took them on barehanded. He received multiple stab wounds and almost died as a result - but his bravery bought precious time for those fleeing the scene.

This week a six-year-old girl from Yorkshire was also hailed as a hero. Olivia Patterson was playing outside with a friend when she saw flames rising from the roof of her house. Olivia ran into the burning building to wake her mother, who was asleep on the sofa with her two younger children.

According to one psychiatrist, Professor Deane Aikins of Yale University, some people are physically prepared for heroism. They feel fear but do not show signs of panic.

While most of us are overwhelmed by a stress hormoneChemicals carried in the bloodstream that alter the way your body's systems act.  in dangerous situations, they experience lower levels of it - and are actually calmed down by another one. He cites as an example Chesley Sullenberger, a pilot who safely landed an airliner on the River HudsonA river that flows through New York. in 2009 when both its engines failed over New York.  

Another psychologist, Dr Punit Shah of Bath University, argues that people who "act quickly and are more impulsive are more likely to engage in acts of heroism... people that are risk-takers."²

The circumstances are also important: "If you're left alone in a situation you're more likely to help - and then whether or not you actually do is decided based upon your personality."

Is courage a little bit mad?

Yes: Human beings have evolved successfully because they have strong survival instincts, which means avoiding danger rather than confronting it. Those who put themselves at risk must be slightly crazy.

No: There was nothing mad about Amy Scott's actions. As Professor Aikins testifies, heroism consists of keeping a cool head and not panicking, which means that it is the very opposite of madness.  

Or... Everyone is different, so it is impossible to generalise. It is probable that Amy Scott acted out of a sense of duty, Olivia Patterson out of concern for her family and Roy Larner out of anger.