Award-winning drug reporter Javier Valdez was shot dead by unidentified attackers on a street near his office in Mexico’s Culiacan on Monday, AP reported. The 50-year-old journalist was the recipient of the International Press Freedom Award given by the Committee to Protect Journalists in 2011. The attack makes him the sixth journalist to have been killed in Mexico this year.

State Prosecutor Juan Jose Rios said investigating officials were considering all possible motives, including a connection to the victim’s coverage of the drug cartel.

At the launch of his book in 2016, Valdez had said, “Being a journalist is like being on a blacklist. Even though you may have bullet-proofing and bodyguards, [the gangs] will decide what day they are going to kill you,” BBC reported.

The reporter covered drug-trafficking and organised crime in Mexico including the influential Sinaloa drug cartel which is believed to be responsible for almost 25% of all illegal drugs that enter the United States via Mexico. The powerful cartel was started by Joaquin Guzman, also known as “El Chapo”, who was captured in 2014 and will soon be on trial in the United States.

The Committee to Protect Journalists’ records show 38 journalists murdered in Mexico since 1992.