Many of the most noxious claims originated in the mind of Mr. Halbig, a retired Florida public school official who became fixated on what he called “this supposed tragedy” at Sandy Hook. Court records and a previously unreleased deposition given by Mr. Jones in one of a set of defamation lawsuits brought against him by the families of 10 Sandy Hook victims show how he and Mr. Halbig used each other to pursue their obsession and promote it across the internet.

Over several years, Mr. Jones gave Mr. Halbig’s views an audience by inviting him to be a guest on Infowars, his radio and online show. Infowars gave Mr. Halbig a camera crew and a platform for fund-raising, even as Mr. Halbig repeatedly visited Newtown, demanding thousands of pages of public records, including photos of the murder scene, the children’s bodies and receipts for the cleanup of “bodily fluids, brain matter, skull fragments and around 45 to 60 gallons of blood.”

Given practical support and visibility by Mr. Jones, Mr. Halbig hounded families of the victims and other residents of Newtown, and promoted a baseless tale that Avielle Richman, a first grader killed at Sandy Hook, was still alive.