Other than what i've read and watched today, i don't know anything about this guy.
According to several sources, including his now removed Wikipedia page, John Mark Dougan was a police officer in Palm Beach, Florida, where he discovered corruption in the sheriffs department involving sheriff Ric Bradshaw. Dougan also claims to be the recipient of damaging evidence regarding the Hillary Clinton-DNC scandal given to him by the now dead Seth Rich. Dougan is apparently responsible for creating the DCLeaks, BurtAaronson (archived) and PBSOTalk whistleblower websites. DCLeaks is dedicated to the Clinton email scandal and PBSOTalk is dedicated to exposing corruption in Palm Beach, Florida.
Dougan's home was raided by the FBI on March 14, 2016, after which he fled to Toronto and finally Moscow where he was eventually granted political asylum by the Russian government. The FBI apparently seized all of his computers during the raid, but Dougan claims to have had a backup of the data.
In an interview with Sarah Westall of Forbidden Knowledge TV, Ex-Cop Has 700 Epstein Blackmail Videos, Dougan claims that he was asked to store information given to him by Joe Recarey, a deceased detective who was working the Jeffery Epstein case. Dougan claims that the archive, in the form of a computer hard drive, contains more than 700 videos totaling around 1.5 terabytes. Of the more than 700 videos, Dougan claims to have watched parts of 7 of them along with a journalist who he claims wanted nothing to do with the material. Dougan claims that 6 of the videos appear to show older men having sex with young, possibly underage woman, and the 7th one shows a young women exiting a shower and applying lotion to her body.
Allegedly in fear for his life, Dougan claims to have distributed more than 10 encrypted copies of the approximately 1.5 terabyte hard drive to people around the world as a 'dead mans trigger' to be released should he be killed.