Mike O'Connor, who was a war correspondent and a advocate for journalist safety in Mexico passed away on Sunday at the age of 67.

The Los Angeles Times Mexico Bureau Chief and wife, Tracy Wilkerson, announced that he died of a heart attack early Sunday morning in bed, reports Deadline.

He had spent the last few years as part of the Committee to Protect Journalists down in Mexico. The nonprofit group works with journalists who are based out of dangerous parts of the country and that face intimidation and worse. If a reporter in Mexico was worried for their life, O'Connor was their contact on how best to deal with the situation and where to go for safety.

A colleague of the war correspondent told KCBS-TV, which he worked for in Los Angeles in the 1980s and 1990s, that O'Connor was a big reason the Mexican Congress pushed through an amendment to their constitution that made it a federal crime to threaten a reporter.

According to the Los Angeles Times, correspondent and Riodoce founder, Javier Valdez Cardenas, said of O'Connor: "He was an activist close to the low-level journalists - the ones in the streets of combat, the ones in the struggle - more than those from the journalistic heights."

Before turning to Mexico, O'Connor spent time as a foreign correspondent in Central America and the former Yugoslavia for the New York Times.