On Sunday afternoon, when Elmer T. Williams’s wife told him that a mass shooting had taken place at a church in Texas, he leapt into action. First, he skimmed a handful of news stories about the massacre. Then, when he felt sufficiently informed, he went into his home video studio, put on his trademark aviator sunglasses, and hit record.



Roughly an hour later, Mr. Williams, 51, a popular right-wing YouTube personality who calls himself “The Doctor of Common Sense,” had filmed, edited and uploaded a three-minute monologue about the Sutherland Springs church shooting to his YouTube page, which had roughly 90,000 subscribers. Authorities had not yet named a suspect, but that didn’t deter Mr. Williams, who is black, from speculating that the gunman was probably “either a Muslim or black.”

Later, after the shooter was identified as a white man named Devin P. Kelley, Mr. Williams posted a follow-up video. He claimed that Mr. Kelley was most likely a Bernie Sanders supporter associated with antifa — a left-wing anti-fascist group — who may have converted to Islam. Despite having no evidence for those claims, Mr. Williams argued them passionately, saying that photos of Mr. Kelley circulating online suggested that he was a violent liberal.

“Sometimes, you can tell a lot from a person’s picture,” Mr. Williams said.

I came across Mr. Williams’s videos several hours after the massacre, when one of them appeared prominently in YouTube’s search results about the shooting, alongside other videos making unverified claims that had been posted by pages with names like TruthNews Network and The Patriotic Beast.