The circumstances of his death were not immediately clear, said the friend, Terrie M. Williams, who had worked with Mr. Shabazz, who was in his late 20s. When asked about the death, a spokeswoman for the United States Consular Service said only that it was “aware of the death of a U.S. citizen in Mexico City.” The New York Amsterdam News reported the death on Thursday. Mr. Shabazz had spent much of his life in and out of both prison and headlines. In 1997, when he was 12, he pleaded guilty to setting a fire that killed his grandmother, Betty Shabazz, a civil rights activist and the widow of Malcolm X, at her Yonkers home. A witness at his trial described him as “a schizophrenic boy of a paranoid type.” He was jailed and released after four years, but was incarcerated again shortly afterward for attempted robbery.