Prosecutors said Wednesday there will be no criminal charges filed against two former Manchester police officers who were fired last year over accusations of sexual assault, witness tampering and criminal mischief. Strafford County Attorney Tom Velardi said there wasn’t enough evidence in either case. Officer Darren Murphy was fired in February. As part of that internal investigation, police said they learned of allegations of misconduct against another officer, Aaron Brown, who was put on leave before being fired in April.