The former Regional Transportation District police chief hired to modernize security on buses and trains has filed a federal lawsuit alleging racial discrimination by agency leaders who knew of “racial animus” against him yet launched a retaliatory investigation after he complained to federal authorities. The lawsuit filed Tuesday in U.S. District Court accuses RTD manager Deb Johnson of discrimination in handling pushback against former RTD Police Chief Joel Fitzgerald, a Black man she hired to overhaul and expand transit security, after he filed a complaint Aug.