A gunman seriously injured three people in the high-speed Amsterdam-Paris train Friday, before he was overpowered by passengers, identified by witnesses as a group of US Marines traveling on the train. He was armed with guns and knives. The motives behind the attack were not immediately known. The two most seriously injured victims are a Briton and an American, whom witnesses say were deliberately sought out for their nationality by the gunman. They are reported in critical condition. The attack happened near Arras in northern France and the gunman was arrested when the train reached the town’s station. The unarmed Marines were said to have overheard the gunman loading a Kalashnikov AK-47 in the toilet. French Interior Minister Bernard Cazeneuve was heading to Arras in the wake of the incident. Officials do not rule out an act of terrorism.