In The Washington Post's continuing investigation, The Hidden Life of Guns, reporter Cheryl W. Thompson offers the first comprehensive analysis of how cop-killers got their guns. "Legal purchase was the leading source of weapons used to kill police officers. In 107 slayings, the killers acquired their firearms legally. In 170 deaths, The Post could not determine how the shooters got their guns, including 29 killings in which weapons were not recovered." Additionally, the analysis showed that traffic stops and domestic disputes are the two deadliest situations for officers.