For two years, Acacia Dietz was a member of the National Socialist Movement (NSM), the largest neo-Nazi organisation in the US.
Acacia was responsible for the NSM’s online presence until a deadly attack in New Zealand shocked the world.
In March 2019, a white supremacist shot dead 51 people after targeting two mosques in the city of Christchurch.
The attacker streamed the shootings live on Facebook.
Although the killings were not directly linked to the NSM, Acacia decided to leave the group in the months after.
UK viewers can watch
In the Face of Terror on Monday 19 October at 21:00 BST on BBC Two and on BBC iPlayer.