Horrific story. On so many levels.
The victim suffered a terrible attack, the people involved were practically children, apparently very troubled children.
Sex by deception is sexual assault.
The filming of the sex act is also appalling.
And yes, this is a mix of vigilante vengeance and transphobia.
Activists have overused the term to the extent it's become meaningless, and this has blurred and obscured a genuine prejudice.
Nobody wins in this scenario.