Washington, DC [US], May 7 (ANI): India should take the matter “very seriously and investigate” said the US State Department speaking on recent allegations associated with the case of the Indian government’s alleged involvement in the killing of the Sikh separatist leader, Hardeep Singh Nijjar. The remarks come at a time when there are already numerous twists and turns to the Nijjar killing case. Responding to a media query during the State Department briefing on Monday (local time) on the arrest of three individuals linked with the killing of India-designated terrorist Hardeep Singh Nijjar, s…