A postmortem exam is being conducted Monday on a 24-year-old Brazilian man who collapsed and died aboard an Irish aircraft Sunday after he bit another passenger.

Cork police arrested a 44-year-old Portuguese woman traveling with the man after discovering five pounds of suspected amphetamine powder in her suitcase.

Sunday night's Aer Lingus flight from Lisbon, Portugal, to Dublin was diverted to the southwest Irish city of Cork, where paramedics pronounced the Brazilian man dead on arrival. Passengers said he had bitten a man sitting near him and crew members sought to handcuff him before he lost consciousness. A doctor and nurse on board failed to revive him.

"The noise he was making was like something I have never heard before. It’s not something you’d hear every day. It was like deep anguish, is the best way I could describe it. Very, very troubled"

- John Leonard, passenger

John Leonard, a passenger on the flight, told Cork’s 96fm that the man’s condition deteriorated after he was restrained.

“After that it got worse I would say, his seizure seemed to get worse,” Leonard said, according to SKY News. “He was actually on the ground shaking violently.

“The noise he was making was like something I have never heard before. It’s not something you’d hear every day. It was like deep anguish, is the best way I could describe it. Very, very troubled. Not screaming in a sense you know if you'd hurt yourself or something, just a very guttural, from deep within him."

Ireland’s police force, known as the Gardai, is hoping the postmortem will show if the man ingested a substance which led him to his frenetic state, according to The Irish Times. Early reports say the man became agitated midway into the two and a half hour flight.

Police were attempting to contact the dead man’s family via the Brazilian Embassy in Dublin, the Times reported. The International Business Times said the man may have been studying in Ireland.

The bitten passenger was admitted to a Cork hospital, while the other 165 passengers and six crew members traveled by bus to Dublin.