A New Hampshire man charged with killing his sister-in-law and two young nephews when he was 16 is expected to be sentenced Friday morning after pleading guilty in August to second-degree murder. Eric Sweeney, now 19, had been living with his older brother’s family in Northfield when prosecutors say he fatally shot Kassandra Sweeney, 25, and her sons, 4-year-old Benjamin and 1-year-old Mason, in August 2022. “The situation had deteriorated the the extent that Sean installed a lock on the door of the master bedroom in order to keep the defendant out of that room,” Durand said. The prosecutor said Sweeney used his brother's handgun, which was kept in a locked safe under the couple's bed. According to court documents, Sweeney left the couple a note when he took their truck in June 2022.