Federal officials say they found a video of the decapitation of a Guatemalan prosecutor in the cell phone of an alleged Zetas cartel member captured earlier this month.
The 50-second video recorded May 24 purportedly shows now-detained Mexican suspect Salvador Arguelles Briones cutting prosecutor Alan Stwolinsky's head off with a large knife.
Photos in the cell phone show Arguelles holding another decapitated head, and a heart close to his mouth as if about to eat it.
Interior Ministry authorities showed the video to The Associated Press over the weekend.
Arguelles was arrested on June 4 with 14 others in connection with the murder of Stwolinsky. His killing is believed to have been retaliation for helping seize 434 kilograms (957 pounds) of cocaine from the Zetas.