Freixo’s investigations have led to the indictment of 225 people, including politicians, police officers and firefighters.
The politician said he was leaving for an unidentified European country with the help of human rights group Amnesty International.
“I plan to stay outside Brazil for a while. I want this time to adjust my security precautions and to call the attention of the authorities,” he told the local media adding that “I’m treating this as my own personal problem but clearly it is a public security problem too.”
Freixo led an investigative commission in 2008 that looked at militias – illegal groups made up of off-duty and former police officers and firefighters who have expanded their presence in Rio’s poorer communities in recent years.
Organized crime within the security forces is among the most serious problems Rio faces as it prepares to host global showpiece sports events – the World Cup in 2014 and the Olympics two years later.
The militias were originally applauded by some politicians as a solution to the drug gangs that dominate many slums but reportedly engage in criminal activities themselves, including extortion and summary executions.
“The threats have always existed but now they have intensified,” said Freixo, who travels in a bullet-proof car, has a 24-hour bodyguard and is widely believed to be the model for the crusading politician in the hit 2010 Brazilian movie “Elite Squad 2.”
In August, gunmen killed a judge who took a hard line against militia members, ambushing her as she arrived home in Niterói, across the bay from Rio. Eleven police officers have been arrested on suspicion of involvement.