In an agitated tone, he explains how his racist views were all a misunderstanding; he would like to talk to his victims – or at least try to – and tell them what was going on in his head.
But as he stares at us, countless questions implode into one: why did he do it?
And the dilemmas remain. Can he be forgiven? How do we forgive what we don't understand? Is it enough just to say sorry?
It's a question haunting South Africa's faltering truth and reconciliation process. Coetzee is one of 149 prisoners short-listed for a presidential pardon that would expunge his criminal record, but the process has released a flood of mistrust and pain which has gushed from a wound deeper than the apartheid past.
It is a wound you still feel sitting with Olga Macingwane in her house in Zwelethemba township, not far from where Coetzee's bomb blew a hole through her life and that of her community.
A frail woman with legs scarred from the blast, Macingwane speaks in a brittle voice about the day late last year when she went to Pretoria and visited Coetzee in prison.
Despite her obvious poverty, in a house with no ceiling that she maintains courtesy of a disability grant, she says she has forgiven Coetzee, and would like others to do the same. "I can say I am happy to have met Stefaans. I told him I forgave him – for myself, not for the other people."
She says her trip to the prison has changed her life in unexpected ways: "You can sit here having a pain, but you don't know who made this pain. Now, when I am having this pain, I know it is Stefaans. I am always saying: 'Oh this is Stefaans making this pain.' It made a change."
Macingwane's empathy is in stark contrast to Coetzee's clinical assessment of his deed: "Immediately after the bomb I felt satisfied, but I was angry about the other bombs," he says, offering a skew smile. "All of us were racist. All of us believed in white supremacy. The race issue was based on our political beliefs."
Macingwane and Coetzee sit uncomfortably on the front line of South Africa's national psyche. Victim and perpetrator, reconciled through their extraordinary meeting, are asking to be taken seriously in a country still darkly cynical about truth and reconciliation.