The son of a couple believed to have been killed in a murder-suicide seven years ago has asked authorities to look at his parents’ deaths with fresh eyes. Mark Sheridan said in a letter to prosecutors this week that a murder-for-hire plot revealed in federal court in New Jersey was “eerily similar” to what happened to his parents, John and Joyce Sheridan, who were found fatally stabbed to death in their home in 2014, which had been set alight. Sheridan and his three brothers have maintained their belief that their parents’ deaths were not self-inflicted. Two men pleaded guilty this week to a fatal stabbing in Jersey City in May 2014, four months before the Sheridans’ deaths, that involved setting the victim’s apartment ablaze. The Somerset County prosecutor’s office has not commented on Mark Sheridan’s letter.