I don't think being trans is part of their beliefs or a requirement to be a member
But all of this may be false information. I would like to hear specifics, if so.
(These aren't actually ideologically motivated killings, oddly enough: in practice they just murder people who slight them, even if "it is imperative and the greatest good that you murder people who slight you" is a key component of their decision-theoretic extremism ideology. Or at least that's how I interpret it.)
And also that the person whom you mention, who was accused of the landlord killing, was in fact married to one of the trans persons above?