CAPE TOWN — South Africa’s most notorious apartheid-era assassin, Eugene de Kock, has received parole after spending 20 years in prison. The government’s decision to let him walk free has unleashed a sort of identity crisis among South Africans. Could a man once known as “Prime Evil” really have changed? Why are we showing such charity to the deadliest cog in apartheid’s racist machine? And more important, why are so many South Africans — mostly white — so angry that this specific prisoner has been freed?

Mr. de Kock was no ordinary inmate, and his crimes featured prominently in the darkest chapters of South African history. After the famous black-consciousness leader, Steve Biko, died in jail in 1977, opposition to apartheid grew. The National Party government realized it could no longer afford the political and economic consequences of activists dying in police custody. So, to continue its dirty work invisibly, a secret counterinsurgency unit was established on a farm called Vlakplaas. In 1983 Mr. de Kock became its commander, and it was from here that he and his men planned the deaths, kidnappings and torture of many anti-apartheid activists.

When former President F.W. de Klerk released Nelson Mandela and lifted the ban on the black opposition parties in 1990, Mr. de Kock was secretly ordered to increase the appearance of black-on-black violence in order to discredit the liberation movements. His squad killed black activists with Russian weapons to implicate the military wing of Mr. Mandela’s party, the African National Congress. They captured black liberation movement soldiers, torturing them until they “turned” and could be used as hit men. This led to a sudden escalation of deaths of black people. In one of his speeches after being released, Mr. Mandela angrily suggested that while the government was talking about negotiations, a “third force” was killing black people. Mr. de Kock and his men were part of that force.

After South Africa’s transition to democracy in 1994, Mr. de Kock disclosed the full scope of his crimes as part of his testimony before the Truth and Reconciliation Commission as both an amnesty applicant and an expert witness. This commission was set up as an example of restorative justice — granting amnesty to perpetrators of violence after they confessed in public. By telling the truth and proving that a crime was committed for political reasons, a perpetrator could receive relief from civil and criminal prosecution. Witnesses and victims of gross human rights violations also testified before the commission, and some received reparations.