Joseph Gilbert Solano, 50, an LA Sheriff's deputy, was fatally shot last year
Rhett Nelson, 30, allegedly shot Solano in back of head at a fast food restaurant
Nelson was also charged with murdering a professional Russian skateboarder
Los Angeles County District Attorney George Gascón took office last Monday
He came into office promising sweeping reforms in criminal justice
Gascón plans to eliminate enhancements that result in longer prison sentences
In Nelson's case, Gascón wants to do away with gun charges
If a judge agrees, Nelson would face 40 years in prison with possibility of parole
Solano's sister, Christina Solano, was outraged, calling Gascón 'disgusting'