re: To win the "whack a mole" game.
The Marine has been removed from combat duty and the incident is being investigated. If it is determined that the wounded man was unarmed and posed no threat, the Marine is in deep trouble. If the wounded man was armed (firearms or explosive), then he may have been a valid target.
Unlike many countries, we do hold our military accountable. There may be a mitigating factor that goes to his state of mind. According to a report I heard on the radio this morning, he had been shot the day before. It doesn't excuse him killing an unarmed man (if that is what happened), but it might be a factor in a court marshal or sentencing.