A constable has been arrested for allegedly threatening the brother of a victim of honour killing,who was gunned down along with his wife in Northwest Delhis Ashok Vihar area in June last year. The deceased Kuldeep (26) and his wife Monica Khari had married against the wishes of their families. Constable Praveen Kumar was arrested after Amit Singh,Kuldeeps brother complained that he was being threatened against testifying in court. According to the police,the couple was shot dead by Monicas brother Ankit and his friends after the former was reportedly mocked by community members for allowing the marriage. The accused,who is posted at the security lines,is a distant relative of Ankit,the police said.