Student unrest on campus continued in the period leading up to the declaration of the second state of emergency on 12 June 1986. The BSS informed the University that it was unlikely that black students would attend lectures on 1 May (Labour Day), or on 16, 17 and 18 June, in recognition of Soweto Day. Although there was no official University policy on ‘making up lost time’, some lecturers rescheduled lectures which they were to have given on sensitive days. Others gave their lectures as scheduled, but repeated them at a later date. Yet others insisted on sticking to the timetable.

On 1 May, a number of students attended a May Day rally in Soweto. After the rally a bus containing about ninety students and some security guards was stopped outside Diepkloof, a suburb of Soweto by troops of the South African Defence Force who ordered the occupants off the bus and almost simultaneously smashed the front doors. Attempting to obey the instruction, the occupants were alighting as quickly as possible, but before many had had a chance to do so a teargas canister was fired into the bus. Terrified students broke the emergency exit window while more teargas was fired at them. Several were injured by broken glass, and many were overcome by teargas. No medical treatment was offered by the SADF, no attempt was made to question the students, and no explanation was given for the action. They were ordered to leave the area about forty-five minutes later.

The acting Vice-Chancellor, Professor R W Charlton, sent a telex to the Minister of Defence, General Magnus Malan, urging him to order an investigation of the incident with a view to taking disciplinary action against those responsible. Although he was able to give the Minister the registration number of one of three Casspirs involved, no action was taken. On 26 May 1988, fifty students and two security guards brought an action against Malan in which they claimed a total of R245 000 in damages. The SADF members denied that they had used teargas, claiming that they had wished only to search the bus for unlawful literature.