ACAPULCO, Aug 22 (Reuters) - A Mexican journalist was shot to death in his car Monday in the Pacific coastal state of Guerrero, authorities said, amid the bloodiest year on record for Mexican media workers.

Columnist Fredid "Fredy" Roman was ambushed Monday afternoon in the city of Chilpancingo by armed attackers on a motorcycle, according to local media.

The journalist was killed just after posting a column on the alleged involvement of local politicians in the disappearance of 43 students in 2014, which investigators called a "state crime" last week.

Roman's death follows the murders of at least three other Mexican journalists this month and at least 18 others so far this year, according to human rights organization Article 19.

Organizations focused on media freedom said they were working to determine whether Roman's death may have been linked to his profession.

This year is already the deadliest for Mexican journalists on record, according to Article 19. Violence against the press has skyrocketed under President Andres Manuel Lopez Obrador's administration, the organization said. He took office in 2018.