Who will prosecute the WANTED Marine on the run???

I just read that this s bag Marine wanted for murdering his girl is probably hiding in Mexico. My question is this..When his sorry *** is dragged back to the USA will he be dealt with by the Military or will the State take him? His fleeing is a federal offense but what I am wondering is which judicial system will kill him sooner rather than later..I dont want numnutz to get off on a technicality of some sort..I myself believe he will or has committed suicide as he is facing double jeopardy..Either way he will never see freedom again..How do they execute cowards in the Military? Any Ideas?? Semper Fi