Reporters without Borders now ranks Mexico as the most risky country in the world for journalists, with nine media professionals murdered in 2016 alone.
Javier Valdez was shot and killed when assailants opened fire on his vehicle in the state capital Culiacan, according to RioDoce, the local media outlet he co-founded and where he continued to work. He was a correspondent for a national newspaper, La Jornada, and also co-founded the respected Riodoce publication and authored several books delving into narcotrafficking and organized crime.
Valdez was one of Mexico's most well-known, and loved, chroniclers of the drug war, winning the International Press Freedom Award from watchdog group the Committee to Protect Journalists (CPJ) in 2011 for his prolific coverage of trafficking and organized crime.
Valdez is the fifth journalist to be murdered in Mexico in just over two months, and the second high-profile reporter to be slain in the country this decade after Regina Martinez Perez, who was killed in 2012.
The news of Valdez's slaying shook Mexican journalists who have already been alarmed by a spike in attacks against the press this year.
Cárdenas was attacked in the state of Sinaloa, where he lived and worked.
But if Valdez's case is anything like that of the many other reporters who have been murdered in Mexico recently, there's a good chance his killers will never be punished.More news: Warriors' Kerr returns to practice for 1st time in 3 weeks
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"Between 2006 and 2016, 21 journalists were murdered with complete impunity in Mexico, putting the country sixth on CPJ's annual index that measures cases where perpetrators remain unpunished", Bello wrote.
Mexican President Enrique Pena Nieto and the USA ambassador to Mexico condemned Valdez's killing.
Reporting on Valdez's killing, Mexican media posted images showing a body lying in the street covered by a blue blanket and surrounded by 12 yellow markers of the kind typically used to flag evidence such as bullet casings.
He revealed that investigators and forensic specialists from Mexico's prosecutor-general's office were on their way to help in the inquiry. The latter chronicled the lives of young people swept up in Mexico's underworld.
Like Valdez, Breach had reported on organised crime, drug-trafficking and corruption.
Mexico ranks third in the world for the number of journalists killed, after Syria and Afghanistan, according to media rights group Reporters Without Borders.
He had written about the Sinaloa drug cartel and its now-detained founder Joaquin "El Chapo" Guzman. Ricardo Sanchez Perez del Pozo, a lawyer with a background in global law and human rights, took over the post.