Witnesses also said the average age of victims of security force atrocities in the former homeland was 16, African Eye News Service reported.
The commission was told how white policemen took their children to the police holding cells in Nelspruit to show them what "terrorists" looked like.
Former detainee Neville Shabangu testifed the policemen on night duty ordered detainees to parade past a glass window, through which the children watched. "While they watched, their fathers told them that 'there are the terrorists'", said Shabangu.
The commission was also told how a former police spokesman, Capt John Walters, who has been on leave for the past year due to work-related stress, personally headed torture and beating sessions of detained pupils and other protesters in 1986.
Shabangu, one of his alleged victims, testified: "This man would lead us to the fifth floor of Nelspruit police station and blindfold us before his friends would join him. Our hands would be tied behind our backs and we would be tortured.
"We could not protect ourselves or even see our assailants. They said we were not co-operating and that the only way we would be able to get out was to die or escape."
Shabangu said on one occasion a group of policemen led by Walters entered a cell containing five detainees and ordered each prisoner to choose a policeman to beat them.
Insisting he had not been an MK member and had never left South Africa for training of any sort, Shabangu said the police had not believed him and had put him in prison for three months.
Shabangu and almost 50 other detainees were released only after a visit from Judge Richard Goldstone, who advised them to lay charges against the police.
"We were released just days after the visit, but I did not lay charges as the very same people who had beaten me were the people I was supposed to report the matter to."
Walters was transferred to a community policing structure after leaving the Security Branch and served as a taxi industry negotiator and press liaison officer in Nelspruit until 1995.
The station's human resources department on Monday said Walters was leaving the police at the end of September for health reasons.
Addressing a news conference at the end of the first day's hearings, commission chairman Archbishop Desmond Tutu said it appeared as if "people went beserk here".
"We have people in a Landrover who chased a group of boys kicking a ball on a field and shot at them.
"The more we listen, the more we realise how lucky we are that people have not gone on a revenge binge."
One woman told the commission how she was shot in the back at a funeral by police and later sentenced to four years in jail for public violence.
"We've seen a pattern of arbitrarinesss where police first shot and asked questions later," Tutu said.
He cited the testimony of a man shot in his own house by a policeman chasing another man.
"I'd never before seen the boy they were chasing, and when he ran into my house, I went after him to see what he was doing," testified Manzini Robert Zitha.
Zitha's leg had to be amputated after he was left lying on a hospital floor for two days without medical care.
The commission also heard how witness Bayeni Annie Silinda's son Frank was beheaded and torched after he was accused of being an informer.
Anah Mthimkulu's husband, Phineas, a former member of the KaNgwane's Inyandza National Movement, was also necklaced by youths at Mangweni Trust.
Mthimkulu was forced to strike a match to set her husband ablaze, but after throwing away the match each time she was given it, the youths took it upon themselves to burn her husband.
Tutu said the alleged collusion between the security forces, medical profession and the legal profession had to be investigated.
Earlier, when opening the Nelspruit herings, Tutu said he was aware people were scared of testifying before the commission, and promised witnesses protection.
"I understand that people are scared to speak before us, but we need to know your stories and will protect you once you have spoken."
According to government officials, a number of witnesses had cancelled their testimony about the activities of the Kabasa gang that operated in KaNgwane townships around Nelspruit in 1986 after two witnesses were killed two months ago.
Officials confirmed on Monday that the commission would concentrate on the activities of the Kabasa gang, which witnesses have said worked with the police and even participated in torturing detainees at police stations.