Warning: Graphic content BATON ROUGE, La. — In a swift move by authorities to keep tensions from boiling over, the U.S. Justice Department launched a civil rights investigation Wednesday into the video-recorded killing of a black man who was shot as he scuffled with two white police officers on the pavement outside a convenience store.A law enforcement official said a gun was taken from 37-year-old Alton Sterling after he was killed early Tuesday in the parking lot where he regularly sold homemade music CDs from a folding table. The official was not authorized to discuss the investigation and spoke on condition of anonymity. It was not clear from the murky cellphone footage whether Sterling had the gun in his hand or was reaching for it when he was shot. A witness said he saw police pull a gun from Sterling’s pocket after the shooting.