Mexican authorities arrested a suspect in the killing of internationally recognized journalist Javier Valdez on Monday night, Interior Secretary Alfonso Navarrete Prida said.

Navarrete said that federal agents in a joint operation had just arrested the “presumed (person) responsible for the killing,” but provided no details.

Valdez was gunned down in a street in Culiacan in the western state of Sinaloa on May 15, 2017.

He was known outside Mexico for his deeply nuanced books about the intersection of drug cartels, politicians and other segments of society. Inside Mexico, he was respected as a veteran journalist who generously shared his knowledge and kept readers informed with a regular column in Riodoce, a publication he helped found.

His killing led to a resounding outcry, but the killings of Mexican journalists have continued. At least 10 journalists, including Valdez, were killed in 2017.

Isamel Bojorquez, Riodoce’s editor and a friend of Valdez, confirmed the news. He said the suspect was arrested in the border city of Tijuana and was a member of an organized crime group. He declined to say which one, but said it had to do with the war that the Sinaloa cartel is in.

Riodoce later reported that Ricardo Sanchez Perez del Pozo, the federal special prosecutor in charge of investigating crimes against journalists, said in an interview that the suspect was a 26-year-old known by the alias “Koala.”

The news site reported that the motive of the killing was related to information Valdez had published weeks before his slaying. Sanchez told the site that the suspect was driving the car that intercepted Valdez. There were allegedly three attackers in the car.

The Sinaloa cartel has been battling within itself and with the Jalisco New Generation cartel for territory in western Mexico, especially since the 2016 capture of Sinaloa’s former leader, Joaquin “El Chapo” Guzman, and his subsequent extradition to the US last year.

The vacuum left by Guzman was contested by his sons and Damaso Lopez, Guzman’s right-hand man. Weeks before his murder, Valdez had interviewed Lopez, the outlet’s first interview of a cartel capo.

“Chapo’s sons found out that we had interviewed Damaso and they pressured Javier (Valdez) to not publish the story,” Bojorquez wrote in a column after his friend’s slaying. “But we refused the request.”

The national security commissioner scheduled a news conference for Tuesday morning.