Seven Royal Marines arrested on suspicion of murder in Afghanistan They can only open fire on somebody if that somebody is a threat to them or if they think that somebody is involved in a hostile act, which could be planting a bomb. The difficulty, he added, came when troops had to "interpret those rules in split second situations." He added: "This will be dealt with by the Service Justice system, and the fact it's happened now may be there was some evidence emerging and the MoD wanted to keep control of this rather than have the story become lurid. It gives them some control over this whole situation. It is understood the Royal Marines were in Helmand between April and September last year as part of 3 Commando Brigade, led by Brigadier Ed Davis. They were based in the districts of Nahr-e Saraj and Nad Ali, a flashpoint for British troops since 2006. An MoD spokesman said: "The Royal Military Police have arrested seven Royal Marines on suspicion of murder.