JOHANNESBURG, South Africa -- The sign language interpreter who stood a few feet from President Obama and other world leaders during Nelson Mandela's memorial service acknowledged Thursday being a schizophrenic with a history of violence. Thamsanqa Jantjie told South African media he had a full-blown episode while he was standing on the stage during Tuesday's memorial, seeing angels flying into the stadium and hearing voices. He said he lost concentration and, as panic rose, kept gesturing. There was nothing I could do. I was alone in a very dangerous situation," he said. I tried to control myself and not show the world what was going on. I am very sorry, it's the situation I found myself in. Asked how often he became violent during schizophrenic episodes, Jantjie said "a lot." He told the Daily Sun newspaper that he sometimes ran around in the streets naked. The episode during the memorial might have been brought on by the momentous occasion or his happiness to be there, Jantjie, 34, told the Star newspaper. Members of South Africa's deaf community had reacted angrily to Jantjie's interpretation, which was broadcast on television, saying his signing made no sense and he did not know the gesture for "South Africa" or "thank you." Instead, they said, he signed the words for prawns and rocking horses. In interviews with South African journalists Thursday, Jantjie said he was deeply embarrassed and terrified his children would see his humiliation. "Life is unfair," he said. This illness is unfair. Anyone who doesn't understand this illness will think that I'm just making this up. He admitted that sometimes he reacted violently during episodes and that he once spent a year and seven months in a psychiatric institution, according to the Associated Press. What happened that day, I see angels come to the stadium. ... I start realizing that the problem is here. And the problem, I don't know the attack of this problem, how will it comes. Sometimes I react violent on that place. Sometimes I will see things that chase me," Jantjie said. I was in a very difficult position. And remember those people, the president and everyone, they were armed, there was armed police around me. If I start panicking, I'll start being a problem. I have to deal with this in a manner so that I mustn't embarrass my country," he said. Eye Witness News reported that he once held a person hostage with a brick at the court where he works as an interpreter. Opposition leaders and critics called on the government to explain who hired Jantjie. Hendrietta Bogopane-Zulu, deputy minister for women, children and people with disabilities, said a mistake had been made using Jantjie and that the owners of SA Interpreters, the company that provided him, had "vanished into thin air." "It's an interdepartmental responsibility," she told AP. We are trying to establish what happened.