A journalist was shot dead in the southern state of Oaxaca on Thursday, the fifth killed this year in Mexico, the state prosecutor's office said in a statement. An official with the Oaxaca state security agency, who requested anonymity, confirmed that the victim was Heber López, director of the online news site NoticiasWeb.

The Oaxaca state prosecutor's office said that two suspects in the killing were in custody and a gun had been recovered from them.

Rodolfo Canseco Gutiérrez, director of the online news site RCP Noticias and a longtime friend of López's, said the journalist covered crime and police news.

Witnesses said that around 6:30 p.m., López was in his office when a white vehicle carrying two men pulled up in front, Canseco Gutiérrez said. One man got out, walked into the office and shot López, he said.

Canseco Gutiérrez said he had just had breakfast with López on Wednesday. He said his friend had never told him he'd received threats, but he didn't doubt the killing had to do with his work.

López's murder follows those of four journalists in January.

On January 31, Roberto Toledo, a camera operator and video editor for the online site Monitor Michoacan was shot by assailants as he prepared for an interview in Zitacuaro, Michoacan.

In the border city of Tijuana, crime photographer Margarito Martínez was gunned down outside his home January 17. On January 23, reporter Lourdes Maldonado López was found shot to death inside her car, also in Tijuana.

Reporter José Luis Gamboa was killed in the Gulf coast state of Veracruz in an attack on January 10.

Jan-Albert Hootsen, Mexico representative of the Committee to Protect Journalists, said on Twitter: "The first six weeks of 2022 have been the deadliest for the Mexican press in over a decade."

Ambassador to Mexico Ken Salazar sent his condolences to the families of the journalists killed this year in a tweet in late January, reiterating the U.S. government's "support for the Mexican forces as they fight impunity."

But as CBS News correspondent Enrique Acevedo reported from Tijuana earlier this month, many in Mexico are asking for more than thoughts and prayers.

A report by the U.S. Department of Justice found that as many as 70% of all the guns used in violent crimes in Mexico are traced back to the U.S.

Mexico's government filed a lawsuit in August 2021 accusing gun manufacturers in the U.S. of "actively facilitating the unlawful trafficking of their guns to drug cartels and other criminals in Mexico."

Thirteen U.S. states and Washington, D.C. have expressed support for the lawsuit brought by the Mexican government.