Marius died from lung cancer, after a long call from Nelson Mandela, thanking him for his sacrifice against the struggle.
An undercover police agent provocateur infiltrated Schoon's group and supplied them with a fake bomb with a view to entrapment.
[2][3] Authorities released Schoon from prison in 1976 having served his full term without remission, with requirements to restrict his movements.
Authorities declared Schoon a "banned" person, which meant he was prohibited from leaving home between 6 PM and 6 AM, and forbade him to teach or associate with other political activists.
[5] The couple feared for their safety in South Africa and moved to Botswana, first to the capital Gaborone, then to Molepolole, teaching at Kgari Sechele Secondary School, and later back to Gaborone where they jointly ran the Botswana branch of the [International Voluntary Service],[6] all the while continuing to work for the anti-apartheid movement.
He was an apartheid government spy named later publicly confirmed as a highly successful infiltrator of the liberation movements.
Later, following a warning from the United Kingdom's High Commissioner (ambassador) in Botswana that Marius was a target for assassination by the apartheid government security forces, the Schoon family moved to Angola via Lusaka, Zambia.