It sounds wierd that his gun has to be held for the robbers' trial, but the surviving robbers can be charged differently, or subjected to a higher sentence because someone died as a result of the robbery. This can be true even if the felony murder statute in Nebraksa doesn't apply (I don't know if it does). The county attorney needs the gun because it is evidence about the death of one of the suspects and he can use that evidence to pursue aggravated charges.