Valdez, 50, was reportedly intercepted by gunmen in Culiacan, the state capital and shot several times not far from the offices of the Riodoce independent newspaper that he founded.
He is the fifth journalist to be killed in Mexico this year.
Valdez received a number of national and international awards including the 2011 Press Freedom Award by the Committee to Protect Journalists (CPJ). He authored several books on organized crime, narco culture and drug trafficking, and wrote for the national daily newspaper La Jornada as well as the news agency, Agence France-Presse.
"In a country where widespread self-censorship is the consequence of violence by drug syndicates and criminal gangs, Valdez still covers sensitive issues," CPJ wrote in its announcement of the award.
Mexican president Enrique Pena Nieto tweeted his condolences for the murder of one of the country’s most famous journalists. "I reiterate our commitment to freedom of expression and the press, which are fundamental to our democracy," he said.
Mexico ranks third in the world for the number of journalists killed, after Syria and Afghanistan, according to media rights group Reporters Without Borders. Since 1992, 40 journalists have been killed in Mexico with the majority of cases going unsolved and unpunished according to a recent CPJ report.
The recent arrests of Sinaloa cartel leaders including Joaquín "El Chapo" Guzman and his former right hand man Damaso Lopez Nunez has further ignited a power struggle in Culiacan among rival groups seeking to fill the void.
Despite attacks and death threats throughout his career, Valdez refused to give up journalism. “To die,” he said in an interview with CPJ, “would be to stop writing.”
