Rivera's personal knowledge of these people, some analysts or critics suggest that his portrayal was evidence of Vidali's and Rivera's involvement in Mella's assassination. Rivera was subsequently expelled from the Mexican Communist Party. In early December 1928, Mella was expelled from the Mexican Communist Party for his association with Trotskyists, but he was readmitted two weeks later. Mella was killed by gunshot in Mexico City on January 10, 1929, an incident believed to be a political assassination. Modotti was by Mella's side as he was shot. She was seen holding his arm, allegedly in a manner similar to her portrayal in Rivera's mural. Vidali is believed to have used the revolver he commonly carried to murder Mella. Modotti was known to keep an M1911 pistol in her house. Officially, José Agustín López (said to have no particular political affiliations) was charged with Mella's murder; two other known criminals, Jose Magriñat and Antonio Sanabria, were also suspects. Police investigators received conflicting eyewitness reports, which are notoriously unreliable. In one version, Mella and Modotti were walking alone, whereas another said that Vidali was walking together with the two. Mella was shot at point-blank range, and neither Modotti nor Vidali were injured. Modotti gave a false name to the investigators, and, although police were suspicious of her alibi, she was released soon after being arrested. Magriñat was also set free: he was ultimately killed in Cuba (allegedly by communists) in 1933 The official position of the present Cuban government is that Mella was killed on Machado's orders. It acknowledges that Modotti was known to have been a Stalinist operative in a number of countries. Some in Cuba continue to believe that Vidali killed Mella. How Machado's men could have operated alone and independently in the highly politicized environment of Mexico City is not explained. According to Abers (2002), both Magriñat and Rivera (who had just returned from Cuba) would have warned Mella that he was in danger. Spanish Civil War Vidali was ordered to go to Spain, where he arrived in May 1936 under the pseudonym of Carlos Contreras. He led efforts to prepare, supervise and coordinate the Antifascist Worker and Peasant Militias (MAOC), organized by the Spanish Communist Party since 1934. This was before the Spanish Civil War broke out. Because he had performed military training in the Soviet Frunze Academy, Vidali, and other comrades such as Enrique Líster, are credited with