I was a high school sophomore, sitting through a business law class, when the principal's voice came over the PA system. It was startling because the interruption was so rare. He said he had some terrible news: President John F. Kennedy had been shot.

I remember the details of that moment, 50 years ago Friday, as clearly as any in my life. Silence fell over the classroom, and shock registered on students' faces. We were anxious for more information but afraid to hear it. Then the principal spoke again: "Let's all bow our heads and pray."

This was a Catholic school, so we had a special connection with our first Catholic president, but I've come to believe the events of Nov. 22, 1963, are ingrained in the memory banks of everyone old enough to have lived through it.

My wife, who attended a public school, remembers the girls in her eighth-grade classroom lowering their heads to their desktops and crying.

My mother was shopping with a neighbor in a department store when they noticed all the other customers had disappeared. "Everyone was in the TV department, watching the news with their mouths open," she said. "When went over there, we were just stunned."

A friend who attended another school said he was having lunch. "I remember Mr. Wallace, one of our instructors, came into the cafeteria to give us the news. We all were in disbelief. There was just stone silence."

What breathes such power into a moment that it remains vivid a half-century later? Was it the jarring realization that no life is safe? Was it unfathomable tragedy in a country so long blessed? Was it remorse at seeing a vibrant leader taken in his prime?

Pleasant Hill Mayor Michael Harris, a student at UC Berkeley at the time, said Kennedy's death struck him so deeply that he still carries scars.

"I was too young to vote because you had to be 21 at the time, but I was very much involved in Kennedy's campaign," he said. "I walked the precincts, I handed out fliers. He was a hero to me.

"His demeanor, his speech, his sense of humor and the way he handled himself were so impressive. It was one of the saddest occasions in my life when he was killed. I compare it to losing my father about 10 years later. That's how strongly it hit me."

Former Walnut Creek Mayor Sue Rainey was a mother of two and in nurse training 50 years ago. She was working a surgical ward on the day of the assassination, so her first instinct was to tend to her patients, but she later reflected on the heartbreak.

"The Kennedys were sort of an American fairy tale," she said. "It was hard to believe anyone would do that to our president."

Contra Costa County Administrator David Twa, then a teenager, said he thinks about the fateful day every Nov. 22. The values espoused by JFK -- "Ask not what your country can do for you" -- and his brother Robert, who was assassinated five years later, inspired Twa to pursue a career in public service.

Those too young to remember may never understand the day's grip on the rest of us, but a friend who was a college student in 1963 may have capsulized it best. Before that dreadful day, he said, he thought our nation was too civilized to let such a thing happen.

That sudden collision with reality was haunting, and it still is 50 years later.

Look for more reflections in the paper on Friday.

Contact Tom Barnidge at tbarnidge@bayareanewsgroup.com.