A Douglas County sheriff’s deputy had a split second to react Friday when he suddenly came face to face with a man holding an assault rifle near an SUV stopped along a suburban roadway. The sheriff’s office on Wednesday released video of Deputy Brad Proux, a six-year veteran, approaching the vehicle and suddenly encountering the driver, who stood with an assault rifle in his hands. Proux shot Deyon Marcus Rivas-Maestas, 25, who has been charged with first-degree assault of a peace officer, said Littleton Police Department Chief Doug Stephens. Investigators do not know why Rivas-Maestas stepped out of the SUV with the rifle in his hands, or why he was stopped on the roadside.