In March 2018, Marielle Franco, a prominent Brazilian human rights activist and politician, was murdered in mysterious circumstances. A champion of the favelas, Rio's slum neighbourhoods, Marielle was also a vocal critic of the city's security forces - both official and unofficial - and the high cost in civilian casualties of their war against Rio's drug gangs. So who killed her and why? And what does the investigation into her death reveal about the state of Brazil today? Juliana Ruhfus went in search of answers. - - Subscribe to our channel: http://aje.io/AJSubscribe - Follow us on Twitter: https://twitter.com/AJEnglish - Find us on Facebook: https://www.facebook.com/aljazeera - Check our website: https://www.aljazeera.com/