• Marius van der Merwe was buried on Wednesday at Medley House in Brakpan. Armed guards and police secured the funeral.

• Van der Merwe was shot dead outside his home after testifying at the Madlanga Commission about police corruption.

Family, friends and neighbours gathered at Medley House in Brakpan on Wednesday to say goodbye to Marius van der Merwe. He was known as "Witness D".

Van der Merwe was a whistleblower. He was gunned down outside his home in front of his wife and children two weeks ago.

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The murder happened just days after he testified at the Madlanga Commission. The commission is looking into political interference in police work.

Security was tight at the funeral. Heavily armed private guards, community policing forum members and law enforcement officers surrounded the venue.

Van der Merwe had made serious claims about corruption and criminal behaviour within the Ekurhuleni Metropolitan Police Department. He had also made serious claims about corruption in other parts of the justice system.

His wife Leanna was overcome with emotion. She paid tribute to him at the funeral.

"Not only are you the love of my life but the father of our beautiful boys. I know that you will live through them," she said.

"Everything you did for the boys and I, we will be forever grateful. My world is shattered and I feel hopeless without you. I love you with every fibre of my being."

One of Van der Merwe's sons also spoke at the funeral.

"I want my daddy to come back," he said.

Family friend Samantha Labuschagne said Van der Merwe was a pillar of the community who worked hard to clean up crime.

"Marius was always on the frontline. We will not stand still. Not the family, not the community, not his friends," she said.

No arrests have been made yet. Police say investigations are ongoing.