Javier Valdez, who won the International Press Freedom Award from the Committee to Protect Journalists in 2011, was shot to death outside his Sinaloa office Monday afternoon.
The Associated Press reports Valdez is at least the sixth Mexican journalist killed in the country this year.
"I went and I checked on the web, and saw that they just shot him..in the middle of the street, as his body was still lying there...as things happen in Mexico with journalists. I'm still in shock," said University of Texas professor Gabriela Polit, a friend of Valdez.
Polit worked with Valdez for one of her books and added she was not surprised by the strong reaction to his death.
"Every time any journalist would go to Culiacan, people will go to him. And he was so generous, he would... show you around. He was warm, generous," said Polit.
In a 2011 interview previewing his International Press Freedom Award, Valdez spoke candidly of the dangers he faced.
"I find myself constantly checking and checking who is behind me, checking my rear view mirrors, and who parks next to me. It's an everyday feeling that can make you sick. I suffer from insomnia. I wake up at night and peek out to the street," Valdez said.
His work focused on drug trafficking and crime throughout Sinaloa, which had attracted previous attention.
The Committee to Protect Journalists reported in 2009, unidentified assailants hurled a grenade into his office, though nobody was injured.
Polit explained that the situation surrounding journalists' safety is far more complex than it appears.
"The violence against journalists in Mexico could be staged as a narco- crime, but that is also a perfect excuse. Because then everything goes to that bag of - oh narcos, which is the bag of impunity," said Polit, who argued that corrupt authorities also deserve blame.
She described the current climate many members of the Mexican media deal with.
"The newspapers are backing off from their (journalists). So if you are in the middle of researching and doing your investigation, you're pretty much on your own," Polit explained. "For journalists to work like that, it's like being thrown into a war without any weapon to defend themselves."
Despite the risks, Valdez and his team at Riodice continued their work.
"I want to carry on living, I want to carry on breathing. To die would be to stop writing," Valdez said in that 2011 interview.
"When you see this amount of injustice, and when you see your friends being killed, and when you see your people are being stepped on- you just cannot turn away," Polit said.
Mexican President Enrique Pena Nieta tweeted about Valdez's death, calling it an "outrageous crime," adding: "The Mexican Government condemned the killing of journalist Javier Valdez. My condolences to his family and colleagues.... I reiterate our commitment to the freedom of expression and press, fundamental to our democracy."
Joel Simon, the Executive Director for The Committee to Protect Journalists released a statement, writing "The Committee to Protect Journalists honored Javier Valdez Cárdenas with an International Press Freedom Award in 2011 to recognize his bravery and uncompromising journalism in the face of threats. His loss is a blow to Mexican journalism and to the Mexican public, who see a shadow of silence spreading across the country."