JOHANNESBURG, South Africa -- Just when it seemed the scandal over the bogus sign language interpreter at Nelson Mandela's memorial had run its course, a cousin and three friends say he was part of a mob that accosted two men found with a stolen television and burned them to death by setting fire to tires placed around their necks.

Thamsanqa Jantjie never went to trial for the 2003 killings when other suspects did because authorities determined he was not mentally fit to stand trial, the four told The Associated Press Monday. They spoke on condition of anonymity because of the sensitivity of the fake signing fiasco, which has deeply embarrassed South Africa's government and prompted a high-level investigation into how it happened.

Their account of the killings matched a description of the crime and the outcome for Jantjie that he himself described in an interview published by the Sunday Times newspaper of Johannesburg.

"It was a community thing, what you call mob justice, and I was also there," Jantjie told the newspaper.

Jantjie was not at his house Monday, and the cousin told AP Jantjie had been picked up by someone in a car Sunday and had not returned. His cellphone rang through to a message saying Jantjie was not reachable.

Instead of standing trial in 2006, Jantjie was institutionalized for a period of longer than a year, the four said, and then returned to live in his poor township neighbourhood on the outskirts of Soweto. At some point after that, they said, he started getting jobs doing sign language interpretation at events for the governing African National Congress party.

Jantjie told the AP that he has schizophrenia, hallucinated and believed he saw angels while gesturing incoherently just 3 feet away from President Barack Obama and other world leaders at the memorial on Tuesday. Signing experts said his arm and hand movements were mere gibberish.

In the interview Thursday, Jantjie said he had been violent "a lot" in the past, but declined to provide details. He blamed his behaviour on his schizophrenia, saying he was institutionalized for 19 months, including a period during 2006.

The 2003 killings, carried out by a grisly method known as "necklacing," occurred a few hundred yards (meters) from Jantjie's tidy concrete home, according to the cousin and friends, one of whom described himself as Jantjie's best friend.

Necklacing attacks were fairly common during the struggle against apartheid, carried out by blacks on blacks suspected of aiding the white government or belonging to opposing factions. But while people who encounter suspected thieves in South Africa have been known to beat or kill them to mete out punishment, necklacing has been rare in such cases.

An investigation is underway to determine who hired Jantjie for the Mandela memorial service and whether he received security clearance. Government officials have not said how long the investigation will take.

Four government departments involved in organizing the memorial service have distanced themselves from Jantjie, telling the AP they had no contact with him. A fifth government agency, the Department of Public Works, declined to comment and referred all inquiries about Jantjie to the office of South Africa's top government spokeswoman, who has only said a "comprehensive report" will eventually be released.

Jantjie told the AP he was hired by an interpretation company that has used him on a freelance basis for years. The address Jantjie gave, however, was occupied by a different company that is not involved in interpreting for the deaf.

The owner of the company, South African Interpreters, was identified by the Sunday Times as Bantubahle Xozwa, the head of a religious and traditional affairs agency of the ANC.

Xozwa told the newspaper that Jantjie was an administrator in his company but was not an interpreter because he was "was disqualified years ago on the basis of his health."

"He was interpreting at the memorial service in his personal capacity," Xozwa said. The ANC has said it had no role in hiring Jantjie for the memorial, but has acknowledged using him at events in the past.

Two ANC spokesmen and a spokeswoman did not answer their cellphones Monday, a public holiday, when AP tried to reach them for comment. A number listed for Xozwa in Johannesburg rang unanswered.

The Deaf Federation of South Africa has said it filed a complaint with the ANC about bogus signing by Jantjie at a previous event where South African President Jacob Zuma was present.

"We will follow up the reported correspondence that has supposedly been sent to us in this regard and where necessary will act on it," the ANC said in a statement last week.

The AP was unable to verify the existence of the school where Jantjie said he studied signing for a year. An online search for the school, which Jantjie said was called Komani and located in Eastern Cape Province, turned up nothing. Advocates for the deaf say they have never heard of the school and there are no known sign language institutes in the province.

Associated Press writer Tsvangirayi Mukwazhi in Johannesburg contributed to this report