PARIS — The two American service members who tackled a suspected terrorist on a high-speed train traveling from Amsterdam to Paris rushed him even though he was fully armed, then grabbed him by the neck and beat him over the head with his own automatic rifle until he was unconscious, one of them said in television interviews here on Saturday.

The suspect entered the train car carrying an AK-47 and a handgun, and “I looked over at Spencer and said, ‘Let’s go,’” said Alek Skarlatos, identified as an Oregon National Guardsman returning from Afghanistan. “And he jumped, I followed behind him by about three seconds. Spencer got the guy first, grabbed the guy by the neck, I grabbed the handgun,” said Mr. Skarlatos, referring to Spencer Stone, a friend and member of the Air Force. The Pentagon confirmed their identities.

Mr. Stone was severely cut by the suspect in the neck and hand and is receiving treatment at a hospital in northern France, though his injuries are not life threatening. An amateur video taken in the immediate aftermath shows the suspect on the ground with his legs in the air, his hands tied, while another man – apparently Mr. Stone, kneels shirtless and evidently in pain. Groans are heard, and a voice saying, “Dude, I tried to shoot him.”