Two young men from Dorchester were held without bail on murder charges on Monday for there Jan. 14 murder of 17-year-old Chad O’Connor on Kenwood Street. The suspects— Richard Sheppard, 19, and Branden Singleton-Legget, 19, were allegedly among a group of men who beat and then shot the victim around 5:30 p.m. on the street. O'Connor was allegedly kicked by Singleton-Legget and then shot in the head by Sheppard, according to prosecutors, who say that video evidence implicates both defendants in the crime. A handgun taken from Sheppard's bedroom is the same calibre as the gun used in the attack, according to prosecutors, who say they are actively investigating the role that other assailants may have played in the incident.