It was very common for southern officers to murder US soldiers of African descent, or the officers assigned to command US colored troops. Pickett murdering US soldiers doesn’t make him unique, I am afraid.
Black union troops were indeed executed after surrendering on several occasions. A case was made that General Forrest bore responsibility for the Fort Pillow massacre, but my understanding is that that case rested on very littl e evidence and was largely refuted.
General George Pickett remains unique for ordering the execution, as deserters, of North carolinians whom he knew had never worn the uniform of any unit of the Confederate Army and who had never joined it.
To learn very little about the case (and nothing about the cuplability of the primary War Criminal, Pickett) other then a weak diatribe against the honor of North Carolinians who fought for the USA, please see the cut-and-paste weak substitute for an argument in post 110 above.