De Vries was shot July 6 following an appearance on a Dutch TV current affairs program, and spent a week in the hospital.
He was recently an adviser and confidant for a witness in the trial of an alleged gang leader and his members, according to the AP.
In a statement, de Vries’s family said he was guided by the belief that “on bended knee is no way to be free.”
His family said he died surround by loved ones and requested privacy “to process his death in peace.”
“We are unbelievably proud of him and at the same time inconsolable,” the family said.
De Vries gained notoriety over the years for his reporting on the disappearances of children, and shining a light on injustice, the AP reported.
He won an international Emmy in 2008 for his work on the disappearance of U.S. teenager Natalee Holloway three years earlier.
“The death of Peter R. de Vries touches me deeply. It is almost impossible to comprehend,” Dutch Prime Minister Mark Rutte tweeted. “My thoughts are with his family, his relatives, friends, colleagues, all those close to him and I wish them a lot of strength in this unimaginably difficult moment.”
Netherlands authorities have arrested and detained two unidentified male suspects, ages 21 and 35, for their involvement in de Vries’s killing, the AP reported.