Updated

A crusading reporter who "breathed, dreamed and lived journalism 24 hours a day" was gunned down as he ate dinner, and colleagues said Tuesday they are certain he was killed because of his work.

Decio Sa, a political reporter for the newspaper O Estado do Maranhao in northeastern Brazil, was at least the fourth journalist slain this year in the South American nation, one of the deadliest for reporters to work in.

"For sure he was killed because of his work as a reporter," Silvia Moscoso, the newspaper's state affairs editor, said by telephone. "Over his at least 17 years at the newspaper he made a long list of enemies, many of whom I imagine would love to see him dead."

"But he denounced so many people and so much corruption that it is impossible to say who was behind his murder," she added.

A gunman fired six bullets into Sa's head and chest in a restaurant in the state capital of Sao Luis on Monday night. He died instantly and the killer fled on a motorcycle driven by an accomplice who was waiting outside, the Maranhao state public safety department said in a statement.

Brazil's National Newspaper Association said on its website that Sa was killed because of his "courageous coverage of crimes committed by hired gunmen."

"He was the fourth journalist to be murdered in Brazil in 2012, highlighting the pernicious effect of the impunity that surrounds attempts made against professionals who work to better inform citizens," the statement added.

The New York City-based Committee to Protect Journalists, or CPR, says on its website that 21 Brazilian journalists have been killed since 1992.

"We've documented a rise in press crimes in Brazil, crimes against journalists, and we're concerned," said Carlos Lauria, Americas program coordinator at CPR.

Brazilian journalists like Sa working outside the big cities like Paulo and Rio de Janeiro are "wide open to attacks," he said.

"The pattern of journalists being killed tells us that those reporting on sensitive issues like local corruption are being targeted and killed," Lauria added.

Last week, the CPR issued its annual "Impunity Index" -- a ranking of nations where the murders of journalists go unpunished, taking into account killings committed from 2002 until the end of 2011. It divides the number of unsolved murders into the total population to create the rating.

Brazil ranks No. 11 on the list. Other Latin American nations are on the list, with Colombia at No. 5 and Mexico at No. 8.

Moscoso, the editor at Sa's newspaper, described him as a "bold, loquacious and extremely friendly and generous reporter who breathed, dreamed and lived journalism 24 hours a day."

She said she never heard Sa mention death threats. But, she added, although "his death shocked all of us, it really did not take us by surprise."

Sa, who was 42, is survived by his wife, Silvana, who is pregnant with their second child, and their 8-year-old-daughter.