Valdez's murder came less than two weeks after a CPJ delegation met in Mexico City with Pena Nieto and other top government officials, and about a month after the killing of veteran reporter Maximino Rodriguez Palacios in La Paz on the Baja California peninsula.
"The Mexican Government must do more to protect journalists and prosecute those criminals who kill journalists for doing their jobs", stated Benavides.
He was the fifth reporter killed since March, making Mexico one of the deadliest countries for journalism at a time when murder rates are at their highest since the peak of the drug war in 2011.
Valdez, a father of two, was at least the fifth journalist killed this year in Mexico, which free-press groups have named as one of the most risky countries for journalists.
Articulo 19 says 105 journalists have been murdered and a further 23 have disappeared since 2000.
On Monday, in an editorial titled "They hit us in the heart", the Riodoce editors wrote, "It's a devastating blow to us, his family, but also to journalism, in Sinaloa, in Mexico, and especially for those who who investigate, write and publish in freedom".
Sinaloa has always been a drug-trafficking hotbed and is home to the Sinaloa Cartel headed by notorious kingpin Joaquin "El Chapo" Guzman, who is in a NY prison awaiting trial on multiple charges.
Mexican President Enrique Pena Nieto and the U.S. ambassador to Mexico condemned Valdez's killing.
A contributor to AFP, Valdez had written extensively for Mexican newspapers about drug gangs in his home state of Sinaloa.
"Even though you may have bulletproofing and bodyguards, (the gangs) will decide what day they are going to kill you".
Valdez's brother, Rafael, said the reporter had been "very happy" in recent days and had not indicated that he had received threats.
In Sinaloa there has also been a fragmentation and power struggle among factions in the drug cartel of the same name following the arrest and extradition to the United States of notorious kingpin Joaquin "El Chapo" Guzman.
"We do not see the violence against journalists stopping", said Balbina Flores, a representative of RSF in Mexico.
Last year, 11 journalists were killed in Mexico overall, it said. "You have to fight to change things'". He reported for the Mexican newspaper La Jornada (Spanish.) He was also a valuable source for global reporters trying to piece together the debacle that is Mexico today.