Flags are at half-staff in Illinois in memory of an off-duty Cook County Sheriff's officer killed last Friday. Authorities say 50-year-old investigator Cuauhtemoc Estrada was shot to death trying to stop two people from robbing his daughter and her boyfriend at gunpoint as they carried food from a car outside a family Christmas party at a VFW Hall in west suburban Bellwood. Illinois Governor Pat Quinn has ordered flags be flown at half-staff from sunrise today through sunset this Saturday. Before joining the police force, Estrada was a Marine who served in Desert Storm. Two 22-year-old men face multiple charges including first-degree murder in the officer's death.