VATICAN CITY (CBSNewYork/AP) — On the ninth day of the 10th month of the seventh year of his reign, Benedict XVI opened a new chapter in church history by ending his pontificate.

He became the first pope in 600 years to resign.

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The Swiss Guards standing at attention in Castel Gandolfo shut the gates of the palazzo shortly after 8 p.m. local time Thursday, symbolically closing the doors on a papacy whose legacy will be most marked by the way it ended — a resignation instead of a death.

PHOTOS: Benedict XVI’s Final Day As Pope

Hours earlier, Benedict emerged from a balcony window at Castel Gandolfo and addressed a cheering crowd for the last time as head of the Catholic Church.

“I am simply a pilgrim who is starting the last part of his journey,” the 85-year-old told the crowd, wearing only a white robe in the chilly evening air.

They shouted back “Long live the pope!”

In attendance was New York Cardinal Timothy Dolan. He told CBS 2’s Tony Aiello that Thursday’s events made a deep impression.

“I just said ‘Look, I love you very much, I’m praying with you and for you. And I’m grateful to you. And that comes not just from me but from the people of the Archdiocese. And he smiled and said ‘Thank you very much. New York — I remember the visit, 2008.’ So it was very moving,” Dolan said.

Benedict arrived at Castel Gandolfo after an emotional sendoff from the Vatican, where his closest aide wept by his side as he bade farewell to Vatican officials gathered in the courtyard of the Apostolic Palace, Swiss Guards standing by at attention.

The helicopter with Pope Benedict XVI aboard flies over Rome on February 28, 2013 in Rome. (Photo: TIZIANA FABI,TIZIANA FABI/AFP/Getty Images)

The helicopter with Pope Benedict XVI aboard flies over Rome on February 28, 2013 in Rome. (Photo: TIZIANA FABI,TIZIANA FABI/AFP/Getty Images)

He traveled by car to the helipad on the top of the hill of the Vatican gardens and boarded a helicopter along with his secretary, Monsignor Georg Gaenswein, for the 15-minute trip to Castel Gandolfo.

From inside his helicopter, he sent out his final tweet to the world from his Twitter account @Pontifex: “Thank you for your love and support. May you always experience the joy that comes from putting Christ at the center of your lives.”

Bells tolled as they took off and circled St. Peter’s Square, where well-wishers held up signs saying “Thank You.”

Before leaving the Vatican, Benedict held his final audience with his cardinals and pledged his “unconditional reverence and obedience” to his successor, a poignant and powerful message to close out his eight-year pontificate, which officially ended at 8 p.m. Thursday.

The pontiff appeared to be trying to defuse concerns about possible conflicts arising from the peculiar situation of having a reigning pope and a retired one.

He also gave a final set of instructions to the “princes” of the Church who will elect his successor, urging them to be united as they huddle to choose the 266th leader of the world’s 1.2 billion Catholics.

“May the College of Cardinals work like an orchestra, where diversity — an expression of the universal church — always works toward a higher and harmonious agreement,” he said.

He said he would pray for the cardinals in coming days as they choose his successor.

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“Among you is also the future pope, whom I promise my unconditional reverence and obedience,” Benedict said in his final audience.

Pope Benedict XVI attends a meeting with his cardinals during a farewell ceremony in the Clementine Hall of the Vatican's Apostolic Palace on February 28, 2013 in Vatican City, Vatican. (Photo by L'Osservatore Romano / Vatican Pool via Getty Images)

Pope Benedict XVI attends a meeting with his cardinals during a farewell ceremony in the Clementine Hall of the Vatican’s Apostolic Palace on February 28, 2013 in Vatican City, Vatican. (Photo by L’Osservatore Romano / Vatican Pool via Getty Images)

Some seemed to choke up at that moment, but the scene seemed otherwise almost normal, with cardinals chatting on the sidelines waiting their turn to say goodbye.

Dolan, who was elevated by Benedict last year, is one of 115 cardinals participating in the conclave to elect a new pope in the coming days. He reflected on what they’ll be looking for in a successor.

“All these other qualities — where they’re from, languages they know, leadership skills, managerial competencies — that’s gravy isn’t it. But boy, you better look for somebody who reminds us of Jesus, which in a way, is another word for you’re looking for a holy man,” Dolan told CBS News correspondent Allen Pizzey.

There are several papal contenders in the wings, including Dolan himself, but no obvious front-runner.

Others include Cardinal Angelo Scola, archbishop of Milan, Cardinal Odilo Pedro Scherer of Sao Paulo, Cardinal Leonardo Sandri of Argentina, Cardinal Marc Ouellet of Canada, head of the Vatican’s office for bishops, Cardinal Antonio Tagle, the archbishop of Manila and Cardinal Peter Kodwo Appiah Turkson of Ghana.

Regardless of who is chosen, Dolan said cleaning up the Church will be a top priority.

“Sadly, tragically, we leaders of the Church have often given people reasons not to have trust in the Church anymore,” he said.

But Dolan said since its founding, the Church has endured many difficult days.

“Those opening years of the Church — tension, difficulties, tough decisions, challenges to meet — as long as it’s done with a posture of confidence and trust, we always get through it,” he told CBS 2’s Tony Aiello.

Benedict’s decision to live at the Vatican in retirement, be called “emeritus pope” and “Your Holiness” and to wear the white cassock associated with the papacy has also deepened concerns about the shadow he will cast over the next papacy.

PHOTOS: Pope Benedict XVI Holds Final General Audience

But Benedict has tried to address those worries, saying that once retired he would be “hidden from the world.” In his final speech in St. Peter’s Square on Wednesday, he said he wasn’t returning to private life, but rather to a new form of service to the Church through prayer.

Dolan expressed gratitude for Benedict’s years of service.

“I have followed your teaching closely. You are indeed a spiritual father to me. You have my love, my gratitude, my prayers,” he said he would tell the pope in their final meeting.

On Monday, the cardinals are expected to begin meeting to set the date for the conclave.

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