Convicted murderer Aaron Hernandez is in trouble once again, getting mixed up in a prison fight, a law enforcement source with knowledge of the incident said Tuesday. Hernandez allegedly agreed to be the lookout for another inmate who went into another prisoner’s cell at Souza-Baranowski Correctional Center. Those two inmates got into a fight Monday, the source says, believed to be gang-related. All three men are being disciplined over the incident, including the former professional football player, who was put in a special management section. Christopher Fallon, a spokesman for the Massachusetts Department of Correction, declined to comment, saying regulations forbid divulging information of that kind about inmates. It’s not the first time Hernandez has gotten into trouble behind bars. While he was awaiting his murder trial, he got into a brawl with a fellow detainee at the Bristol County jail. On Thursday, a judge may set a trial date for Hernandez’s double-murder trial in Boston for deaths that occurred in July 2012. Hernandez, who formerly played for the NFL’s New England Patriots, was sentenced April 15 to life behind bars in the shooting death of Odin Lloyd in June 2013.