Three activists who attended or promoted the Michael Brown events in the three cities said they were promoted by local chapters of the Black Lives Matter movement and in local email newsletters. The three people asked to not be identified because they feared being targeted by online trolls and they were embarrassed by their involvement with the Black Elevation Facebook page.

The Black Elevation page was identical to other activist pages, down to the videos calling on the public to oppose racism, they said.

No public evidence of those videos remains, but Mr. Albright was able to find at least two videos that were once posted on Facebook — one had 2.5 million views and the other about one million. One of the activists recalled a Black Elevation video being shared by several of his Facebook friends and said he joined the group shortly after viewing it.

Another activist, who is a student at a university near Atlanta, said she joined the Black Elevation page when she noticed a paid advertisement for it on Facebook. The social media company confirmed that the group placed advertisements, though it would not reveal what demographic was the target or how much was spent on ads.

In one of the few details offered about the page, Facebook said the group ran an advertisement seeking to hire an event coordinator. The ad for the part-time position, which was liked more than 1,000 times and shared nearly 300 times, promised payment in two parts, before and after the event.

A student activist in New York said he applied, and was interviewed for the job over Facebook’s Messenger app. He did not recall the name of the person conducting the interview, but said the interviewer asked few questions and made frequent spelling mistakes. He did not follow up afterward, and he said he was never contacted by the group again.