Attorney General Eric Holder pays his respects at the grave of John F. Kennedy at Arlington National Cemetery on Friday, the 50th anniversary of Kennedy's death. (Jacquelyn Martin/AP)

The motorcade swept into Arlington National Cemetery just before 7 a.m. Friday, bringing Attorney General Eric H. Holder Jr. to the burial site of the president who was assassinated when Holder was just 12.

Holder remembers taking a test in seventh-grade science on the morning of Nov. 22, 1963, after hearing impossible-sounding rumors in the hallway: President Kennedy shot in Dallas? How could that be?

But his science teacher kept darting out of the room while the kids scribbled their answers, a Justice Department spokeswoman who relayed Holder’s recollections said Friday. When the teacher returned to the classroom, his eyes were red. The test ended, and the teacher relayed the terrible news.

What else does Holder remember? Coming home from school, the spokeswoman said. It was the first time he ever saw his father cry.

And so, on the 50th anniversary of the assassination, Holder stood alone, head bowed and hands clasped, at the site where John F. Kennedy and his wife, Jacqueline Kennedy Onassis, are buried, along with their son Patrick, who died in infancy, and a daughter who was stillborn and never named.

The eternal flame that marks the site burned yellow-white. The dark sky lightened into deep blue clouds, floating in the glow of a pink sunrise.

Holder placed a Justice Department commemorative coin near Kennedy’s polished marker, then walked a short distance to the grave of Robert F. Kennedy, the president’s brother and former attorney general, who was assassinated five years later. The nation’s current chief law enforcement officer left a commemorative coin at Bobby Kennedy’s grave, too.

The cemetery visit, five minutes in all, was a quiet beginning to a day of commemorations and reflections marking the passage of 50 years since a U.S. president was assassinated.

Two British bagpipers from the Royal Highland Regiment played shortly before 8:30 a.m., and Kennedy’s sister, former ambassador to Ireland Jean Kennedy Smith, laid a wreath. Additional events were planned in Boston, where Kennedy was born, and Dallas, where he was killed. It is the first time the Texas city has held an official commemoration on the anniversary of Kennedy’s death. President Obama ordered that flags across the nation be flown at half-staff.

In Dallas, Kennedy was honored Friday with a ceremony that featured speeches by the mayor and other dignitaries, performances by the U.S. Naval Academy Men’s Glee Club, a moment of silence and the unveiling of a memorial inscribed with the last lines of an address that the president was supposed to deliver to Dallas leaders on the day he was killed.

“We in this country, in this generation, are by destiny rather than choice the watchmen on the walls of world freedom,” Mayor Mike Rawlings said, reading from Kennedy’s undelivered speech as a light rain fell on the gathering at Dealey Plaza, the site of the assassination. “We ask, therefore, that we may be worthy of our power and our responsibility . . . and that we may achieve in our time and for all time the ancient vision of peace on earth, goodwill toward men.”

Rawlings spoke in front of the uniformed Naval Academy midshipmen, with a huge banner bearing Kennedy’s image and “JFK” hanging in the background. Also participating in the ceremony were a military color guard, bagpipers and Dallas religious leaders.

The memorial site at the military cemetery in Arlington drew a steady stream of visitors all morning. They left bouquets of red and white roses, orchids and wreaths. The Moroccan ambassador to the United States brought a wreath of red roses on behalf of the king.

Timothy Barton, 72, came with his daughter from Manchester, England, a trip booked at the last minute. The pair visited Dallas 20 years ago to mark the 30th anniversary of the assassination.

“It’s very special to be here,” Barton said. “He was loved the world over by hundreds of millions of people.”

Nearby, Michael Poe of Tampa snapped a picture of the eternal flame. In Washington for a conference of audiologists, he made the short trip from his hotel after seeing news reports that showed there were few people at the site. “I wanted to come out of respect,” Poe said. “Out of the dreams and goals this man set.”

Poe remembers vividly where he was when he heard Kennedy had been shot — sixth-grade English class in Bellington, W.Va. He recalled the normally stern principal shedding tears as he told the kids the president was dead. Go home, the principal said. School is closed for the rest of the week.

Matla Pritchard, 61, of Ontario also remembers the unusual classroom interruption by a solemn elementary school principal. She wept Friday morning as she stood with her husband several feet from the memorial, recalling the “incredible shock and sadness” of that day.

Kennedy “was a remarkable man,” Pritchard said. “He contributed so much to the world, and the vision of peace in the world.”

See complete JFK coverage

Read: Four shattering days

Read: Dealey Plaza: The scene of the crime

Read: A widow’s enduring legacy

William Branigin contributed to this report.