Columnist Fredid "Fredy" Roman was shot to death in his car on Monday in the state of Guerrero, Mexico, according to authorities.

Roman was ambushed by armed attackers on a motorcycle, local media reports.

He had posted a column alleging local politicians were involved in the Ayotzinapa case, where 43 students disappeared in 2014.

Human rights organization Article 19 says Roman is at least the 18th journalist murdered in Mexico this year.

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