At the time of the event, a year after World War II, he was still engaged in work on nuclear bombs. On May 12th 1946, he, together with seven other scientists, was working on small pieces of plutonium, assembling them to make a larger mass, which once formed would undergo a chain reaction and become radioactively explosive. With the usual nonchalance of an expert he was manipulating the pieces slowly together using a screwdriver. Unfortunately the screwdriver slipped and the pieces came together unexpectedly, undergoing a chain reaction and releasing huge quantities of lethal radioactivity into the atmosphere. It is at this point that Slotin exhibited the qualities Bronwski considers quintessential for morality. Recognising the immediate danger, he swept aside the pieces of plutonium with his hand. It was a split second decision, but he chose to protect the lives of his colleagues over himself. He then called for medical help and asked the rest of them to mark exactly where they had stood during the exposure so as to be able to pinpoint the amount of radioactivity in those areas and hence the possible damage. He also told them that he would probably die but he thought they would recover. His words were all too accurate. Slotin died nine days later from radioactive sickness.
The idea of morality put forward by Bronwski is something I feel is very accurate.