Johannesburg - Convicted killer Frikkie du Preez, one of the so-called "Waterkloof four", was released on parole on Friday, correctional services said."The department can confirm that the offender has been released on parole as per order of the parole board," spokesman Logan Maistry said.He said if an offender had served half their sentence, they were eligible for parole."If the offender violates the parole conditions, they will be put back into custody."The "Waterkloof four" - Du Preez, Christoff Becker, Gert van Schalkwyk and Reinach Tiedt - beat, stabbed and kicked a homeless man to death in Moreleta Park, Pretoria, on the night of 1 December 2001. The victim was never identified.They were found guilty of murder in June 2005. In May 2008, the North Gauteng High Court in Pretoria rejected their bid to appeal.They were released on bail on 11 February this year, after serving five-and-a-half years of their 12-year jail terms.Du Preez and Becker's parole was revoked when a video emerged of the pair drinking what appeared to be alcohol and using a cellphone in the Kgosi Mampuru prison where they were serving their sentence.The pair was sent back to prison on 28 February.Becker was released on parole on Tuesday.