The man shot and killed by a police officer in Lexington, Massachusetts, has been identified as Colin Barthelemy, 26, according to the Middlesex County District Attorney's Office. The shooting occurred on April 19 after a caller reported their son had hurt himself. Police responded to a home after two people were escorted from the house by their parents. At some point, police say Barthehelemore came out of the house with a large kitchen knife and officers twice tried to use non-lethal force but couldn't stop him. The district attorney's office said a North Eastern Massachusetts Law Enforcement Council (NEMLEC) member from Wilmington fired the fatal shot, which was taken to the hospital as a precaution. The incident remains under investigation.