Baldwin, as producer, hired a non-union gun handler for his movie production.
Not clear that they were non-union, just not a member of the Hollywood local.
Baldwin is partners with the writer/director.....that was shot. Eventually what happened will all come out.
The answer may be less nefarious, but I can’t help but wonder if - if the propmaster is not a union member - some self-appointed union activist might have set up this scenario as a means of condemning the hiring of a non-union crew member.