Parker, age 24, and Ward, age 27, died at the scene while Gardner survived.
The gunman was identified as 41-year-old Vester Lee Flanagan II, also known by the professional pseudonym of Bryce Williams, a former reporter at WDBJ.
Office memos from WDBJ showed that in July 2012, Dan Dennison, the station's then-news director, ordered Flanagan to contact Health Advocate after complaints that coworkers were "feeling threatened or uncomfortable" while working with him.
Flanagan was dismissed by WDBJ on February 1, 2013, because of his volatile behavior.
Flanagan allegedly threw a wooden cross at Dennison, saying "You need this." Flanagan filed an EEOC complaint against WDBJ, alleging racial discrimination. Following an investigation, the EEOC dismissed the complaint as uncorroborated.