Mexico - A prominent Mexican journalist reported on Wednesday that the sons of Sinaloa cartel kingpin Joaquin "El Chapo" Guzman say they were attacked and wounded by a rival drug gang figure and onetime "top lieutenant" for their father.Ciro Gomez Leyva said he received word about Saturday's purported attack in a handwritten letter from Guzman's sons that said they were with Sinaloa boss Ismael "El Mayo" Zambada at the time and he was also targeted.Gomez Leyva said the letter accused Damaso Lopez, another alleged Sinaloa figure who is believed to be disputing for control of the cartel, of betraying them. The letter said they had come to a meeting organised by Lopez only to find he was not there, and gunmen suddenly opened fire and killed their bodyguards. Guzman's sons said they and Zambada escaped.Guzman lawyer Jose Refugio confirmed to local media that the letter came from the sons."I was aware of that, I know about that letter and I know they wrote that letter," Refugio told Radio Formula. "But it was not delivered through me."Mexican authorities did not immediately confirm or otherwise comment on the purported attack.Guzman was arrested for the third time in January 2016 and finally extradited to the United States last month. Some have speculated a bloody turf war could break out to fill the power vacuum.Last August, his son Jesus Alfredo Guzman Salazar was one of a half-dozen people kidnapped by armed men from a restaurant in the Pacific coast city of Puerto Vallarta. He was released not long afterward.According to the US Department of Justice, Lopez was indicted by a federal grand jury in Alexandria, Virginia, in 2011, accused of conspiracy to distribute cocaine and conspiracy to launder money.When the indictment was unsealed on March 7, 2013, he was said to be 47 years old. At the time, the Department of Justice called him "a top lieutenant" for Guzman and the Sinaloa cartel.