Jody Armentrout was sitting at an exit row seat on Saturday’s All Nippon Airways Flight 114 traveling from Tokyo to Houston when he noticed a man was acting strangely.

Armentrout, who has served in the Marines for over 20 years and is based in Japan, has been trained to be vigilant. He said he saw the man take his backpack to one of the bathrooms, then come out and go to another bathroom, and then, another bathroom.

“He came out of that one and began pacing up and down the aisle, so that just threw my radar on,” Armentrout, 50, said in a phone interview.

But then, Armentrout said, he saw the man eyeing up the emergency exit right next to him. Armentrout said he stood up, putting himself between the man and the exit door.

That’s when the man turned around, ran through the plane’s galley and darted to the exit door on the opposite side, Armentrout said. The sergeant major knew he had seconds to act.

“He grabbed a strap around the door, pulled it off, and about that time is when I took him and slammed him, put him on the ground,” Armentrout said. “And then there was an older gentleman sitting on that side that woke up, and he got up and kind of helped me.”

Armentrout said flight attendants handed him zip ties, which he placed around the man’s wrists and used to secure him to a seat. It was announced that the plane would be diverted to Seattle as a result of the incident, and Armentrout said he sat next to the man until they landed at Seattle-Tacoma International Airport.

“His eyes — you could definitely tell there was something going on,” Armentrout said.

All Nippon Airways Flight 114 departed from Haneda Airport Saturday morning and was heading to Houston’s George Bush Intercontinental Airport when a passenger became “unruly,” according to the airline. Port of Seattle Police told NBC News that the passenger was attempting to open exit doors during the flight.

Police confirmed that passengers and flight crew restrained the person, who has not been identified.

The flight landed at Seattle at 4:19 a.m. PT, and the man was taken off the plane, police said. He was evaluated and it was determined he was “having a medical crisis,” according to police. The man was later taken to a local hospital.

Armentrout said he acted out of concern for his fellow passengers, especially multiple babies who were on board.

“I just knew he was up to something crazy, and at the end of the day, I was willing to take the risk of him saying, ‘I’m not doing anything’ and then just them making him go sit back down, than me allowing him to do anything that’s going to put anybody at risk,” Armentrout said.

Other passengers on the flight took the time to thank Armentrout for taking action when he did, he said.

But the eventfulness of the flight did not stop there. Once on the tarmac in Seattle, another passenger who “was frustrated at the flight diversion” punched a bathroom door, according to the FBI’s Seattle field office.

That person, who has not been identified, was removed from the flight, which eventually landed in Houston at 12:42 p.m. CT, according to FlightAware.com.

After finally arriving in Houston, Armentrout said he was glad his feet were on the ground.

“It was a weird flight,” Armentrout said, adding that he will be returning to Japan on Friday and is feeling a little anxious about the journey.

Keeping in mind what happened, Armentrout wants others to stay aware of their surroundings.

“I want to make sure everybody understands what time we are in, in this world nowadays, and that they need to be aware of their surroundings all the time,” he said.