A group of U.S. Marines on a French train thwarted a potential terror attack as it began.

“A man opened fire on this Thalys train between Amsterdam and Paris, one person was very seriously injured,” Pierre Henry Brandet, the French interior ministry spokesman, said.  While Brandet played down a potential terrorist angle he admitted the investigation has been turned over to anti-terror authorities.

According to witnesses, the Marines heard the gunman in the bathroom, loading his weapons and were able to stop him after he wounded three people.  Two of the injured are reported to be in critical condition.  Witnesses say two of the wounded, an American and a Briton, were hurt as they subdued the attacker.

The gunman was identified as a 26-year-old Moroccan who was known to anti-terror authorities in the country.  He was armed with a Kalashnikov rifle and a knife.

“The situation is under control, the travellers are safe. The train stopped and the emergency services are on site,” the Thalys official Twitter account tweeted.