The flight captain raced up the aisle screaming about bombs, pounded on the cockpit door and shouted, "First Iraq, then Afghanistan, now this," passengers said Tuesday. "We all knew in the front rows if he got back in the cockpit, we were going down," said Gabriel Schonzeit, who witnessed the drama from a third-row seat aboard JetBlue Flight 191, which made an emergency landing at Rick Husband Amarillo International Airport at 10:11 a.m. More than a half-dozen passengers, many on their way from New York to Las Vegas for a security convention, surged forward and subdued the captain, he said. Airport officials identified the pilot as Clayton Frederick Osbon, 49, of Richmond Hill, Ga. When the plane touched down, Amarillo police scrambled aboard, apprehended Osbon and transported him to Northwest Texas Hospital, officials said. JetBlue Airways officials said in a statement the flight captain suffered a medical condition and another pilot who was onboard but not on the crew stepped in to help fly the plane. Airline officials would not elaborate. The FBI is investigating.Several hours into the flight, passengers said, Osbon emerged from the cockpit, walked into the bathroom at the back of the plane, then sprinted up the aisle, screaming "Iraq," "al-Qaida" and "terrorism." He tried to re-enter the cockpit, but his security code appeared to have been changed, Schonzeit said."It seemed like he went crazy," Schonzeit said.Flight attendants sought to calm Osbon as he stood with his hands trembling, but he steadily became more agitated, Schonzeit said. He attempted to use the intercom, but it appeared to have been disabled, said Josh Redick, 41, of New York.Finally, when Osbon moved toward a side door yelling about Iraq and Iran, ex-prison guard David Gonzalez, 50, of New York, and others acted, passengers said. "'I'm going to show you what Iraq is,'" Gonzalez said he told the pilot. The men struggled as others arrived. "Once I got him in a choke-hold, he got real weak."A half-dozen to 10 passengers took Osbon to the floor, passengers said.Four men held him down. The passengers tried to bind Osbon's wrists behind his back with a zip tie, but he broke it, Schonzeit said. "I couldn't have broken those," Schonzeit said.Paul Babakitis, a former New York police sergeant, said he and the other men holding Osbon asked passengers for their belts to bind his arms. The men held Osbon until the Airbus A320 landed at Amarillo, Babakitis said. Gonzalez estimated that stretch to have covered about a half-hour.Shonzeit, who stands 6 feet, 3 inches and weighs 250 pounds, described Osbon as an exceptionally large man. Shonzeit said the pilot appeared to be an inch taller than him and looked to weigh about the same as him.When Amarillo police boarded the plane, Babakitis grabbed a pair of handcuffs from an officer and locked them onto Osbon's left wrist, he said."Kudos go out to the co-pilot who locked him out," Babakitis said. "He wanted to take the plane down."Glenn Wolk, of Long Island, N.Y., said he had been watching an in-flight movie when it happened. "I felt bad for him," Wolk said.Federal officials verified much of the account from passengers.The plane's co-pilot "became concerned that the captain exhibited erratic behavior," according to a preliminary investigation by the Federal Aviation Administration."The captain had exited the cockpit during the flight, after which the co-pilot locked the door," agency spokeswoman Brie N. Sachse said. "When the captain attempted to enter the locked cockpit, he was subdued by passengers."Passengers expressed dismay there was no federal air marshal aboard.Authorities would not disclose where Osbon was Tuesday night.Passengers deplaned and went through security checks with their carry-on luggage. During the check, authorities brought in a canine unit to search passengers' bags. The passengers later continued their trip on another plane. Six crew members and 135 passengers were aboard Flight 191 when it took off at 7:28 a.m. from John F. Kennedy International Airport in New York, airline officials said.Federal airport officials directed all inquiries to JetBlue."It seems to be more of a medical issue than a security issue at this point," said Transportation Security Administration spokesman Luis Casanova.The flight's passengers will be reimbursed for the flight and receive a credit for twice the value of their tickets, according to a JetBlue news release.It was unclear which security convention the passengers were bound for. International Security Conference West 2012 was scheduled to get under way in Las Vegas with a bonus education event Tuesday. The conference was set to continue through Friday at the Sands Expo and Convention Center, according to the ISC West 2012 website. This was the second flight in about five months to make an emergency landing in Amarillo because of an unruly person onboard. Prosecutors said Ali Reza Shahsavari, 29, of Indialantic, Fla. caused Southwest Airlines Flight 2683 to make an emergency landing in October after he became "disruptive, screaming profanities, and entering and damaging the lavatory of the aircraft," a federal indictment said. Earlier this month, a judge determined Shahsavari was competent to stand trial.Staff writers Bobby Cervantes, Karen Smith Welch and Russell Anglin contributed to this report.