Journalists such as Harlan McKosato attributed the split to Means and other AIM members dividing over opposition to the Bellecourt brothers because of their alleged involvement in the execution of Anna Mae Aquash in December 1975 , who was then the highest @-@ ranking woman in AIM but had been suspected of being an informant . It was a year in which other FBI informants had been discovered in AIM . On November 3 , 1999 , Means held a press conference in Denver , Colorado in which he accused the Bellecourt brothers of complicity in Aquash 's death , and named three lower @-@ level AIM members involved in her death : Arlo Looking Cloud , John Graham , and Theda Nelson Clark . This was the first time that an AIM leader active at the time of the Aquash murder had publicly accused AIM of having been involved .