But footage from the scene showed there were other instances of heroism that day: A retired mechanic rushed one of the attackers and grabbed his weapon. Later, another man ran up and threw an object at the same attacker. Lifeguards at the world-famous beach also headed to the area while the assault was under way. The attack on a Hanukkah celebration by two shooters, which killed 15 and wounded several dozen, shocked the world. But the extraordinary acts of a number of people on the scene heartened many in Australia and beyond. Their actions raised a question: How can ordinary...