What characterizes the administrators (or admins) of social media groups dedicated to social change and protest against institutional injustices? The article analyses the characteristics of such admins using the activism for justice for Roman Zadorov in Israel as a case study. The findings demonstrate a phenomenon of ‘ad-hoc activism’: The background of the admins is heterogeneous, with most having no history of activism before their involvement in the activism for justice for Zadorov. In addition, these admins have negligible involvement other activism causes – they gather ‘ad hoc’ only through justice for Zadorov activism. The socio-demographic and other characteristics of the admins are discussed. Implications regarding the character of contemporary online activism and of the people leading it are discussed.