According to a preliminary internal report circulated inside the Bureau of Alcohol, Tobacco, Firearms and Explosives, federal and local officials recovered ammunition with the rifle that appeared to be engraved with statements “expressing transgender and anti-fascist ideology.” But a senior law enforcement official with direct knowledge of the investigation cautioned that report had not been verified by A.T.F. analysts, did not match other summaries of the evidence, and might turn out to have been misread or misinterpreted. In fast-moving investigations, such status reports are not made public because they often contain a mixture of accurate and inaccurate information.