Ron Clifford, an Irish man who survived the 9/11 terrorist attacks at the World Trade Center, has died suddenly in his home in Connecticut, according to reports.

Clifford, who was originally from Cork, was on the ground floor of the World Trade Center when the first plane hit the North Tower on September 11, 2001.

He survived the attacks uninjured but later discovered that his sister Ruth Clifford McCourt and her four-year-old daughter Juliana died on board one of the planes that crashed into the World Trade Center. 

Clifford died suddenly at his home in Connecticut on Friday night, according to RTÉ News. 

Clifford spent many years campaigning to have those who masterminded the 9/11 attacks brought to justice and previously told RTÉ that he was angry at the failure to bring the perpetrators of the attack to justice. 

Speaking to RTÉ with his brothers Mark and John on the 20th anniversary of the attacks in September 2021, Clifford expressed hope that he would get his "day in court". 

"The justice system here has just prevented it and it's just going around in a circle for years and years," Clifford told RTÉ in September 2021. 

"I hope in our lifetime we will get our day in court." 

He added that his family had learned to cope with the impact of the 9/11 attacks over the past two decades. 

Clifford also featured prominently in the first episode of "9:11: One Day in America", an award-winning six-part docuseries produced by the 9/11 Memorial Museum and National Geographic to mark the 20th anniversary of the attacks. 

Clifford detailed how he bravely assisted a woman who suffered severe injuries during the attacks and later discussed the heartbreak of learning that his sister and niece had been killed in the attack. 

Clifford's funeral details have yet to be announced.