The Committee to Protect Journalists called on Brazilian authorities to conduct a thorough investigation into Vieira's killing and to promptly bring to justice all those responsible.
Three unidentified men in a light-colored compact car intercepted Vieira's vehicle outside the offices of Bezerros FM, a local radio station owned by Vieira, in the city of Bezerros, 67 miles (107 kilometers) from the state capital of Recife, according to the national daily O Globo.
Witnesses quoted in the local press said one of the assailants walked over to Vieira's car and shot him three times in the chest and head before fleeing. Vieira was taken to a local clinic and then transferred to a regional hospital in the nearby city of Cuararu, where he was pronounced dead.
Vieira, 40, hosted the radio program "Bezerros Comunidade," which focused on local social issues, O Globo reported. He also owned the local newspaper Folha do Agreste and a music production company.
Local police are investigating the killing, and authorities have offered a reward of 2,000 reais (US$ 1,200) for any information on the crime, according to news reports. Investigators told local reporters that Vieira's murder appears to be an execution by hired gunmen. They do not have a motive yet, but said they had not ruled anything out.
"We are saddened by the death of José Givonaldo Vieira, and offer our deepest condolences to his family, colleagues, and friends," said Robert Mahoney, CPJ's deputy director.
"Brazilian authorities must conduct a prompt and thorough investigation into Vieira's killing, and determine if he was targeted in retaliation for his work in journalism. All those responsible for Vieira's death must be brought to justice."
In 2009, Brazil was included for the first time in CPJ's Impunity Index, a list of countries where journalists are killed regularly and governments fail to solve the crimes.
CPJ research shows that while Brazilian authorities have succeeded in prosecuting some journalist murders, those efforts have not offset the nation's high rate of deadly violence against the press.
Five murders have gone unsolved in the last decade. In a 2006 special report, "Radio Rage," CPJ found that radio hosts and independent journalists are the most common victims in Brazil's remote Northeast, where political influence permeates radio news.