You can bet some leftist group/individual is behind him, needs to be outed.
I’ve said before that there is some inflammatory literature and a list of organizations to target, if not on his person at the time then at his residence. They’re closing ranks and will stonewall to prevent disclosure. His computer needs to be seized as evidence and any organizations that may have inflamed him need to be raked over the coals in a very public way. I will be very pleasantly surprised if that happens, though.