The scene was horrific. A man laying in a pool of his own blood, alongside a mangled motorcycle. His left leg was almost severed below the knee. That’s what Fullerton Police Cpl. Matt Wilkerson faced when responding to a call of an accident at Commonwealth and Basque Avenues on the evening of Aug. 22. “He was still conscious but I knew that time was very short,” Wilkerson said. Wilkerson didn’t know it at the time, but the victim was Nick Wiltz, then 24, an off-duty Los Angeles police officer, who had just left the home of his girlfriend’s family nearby.…