The group chose as its neighborhood watch coordinator the very man who had invited the official to speak: a man with thinning dark hair and an average build named George Zimmerman. The next month, the newsletter for the homeowners association included a cartoon of a man peering through a magnifying glass, à la Sherlock Holmes, next to a call for help: “We have recently experienced an increased incidence of crime within the community, including three break-ins in the past month, which is why having residents committed to being members of the Neighborhood Watch and reporting suspicious activities is so important. We must send a message that we will not tolerate this in our community!”

To get involved, the newsletter said, “Call George Zimmerman.”

From Virginia to Florida

Now, on this dark, wet night, the neighborhood watch coordinator for the Retreat at Twin Lakes — armed with a licensed, slim 9-millimeter handgun that he kept in a holster tucked in his waistband — was in his truck when he noticed a hooded figure walking through the complex.

He may have been about to go on an errand to Target, as he later told his family, but his commitment to vigilance kicked in. This, it seems, was part of who George Zimmerman was.

He, too, was from someplace else — the second of three children raised in a red-brick home in a cul-de-sac in Manassas, Va. His father, Robert, was a magistrate judge and a veteran of the Vietnam War, and Robert’s father worked in Army intelligence. His mother, Gladys, a Peruvian immigrant, worked as a deputy court clerk. They ran a disciplined household that emphasized service, responsibility and the Roman Catholic faith.

“Some kids would have said, ‘That’s like a prison,’ ” recalled George W. Hall, a retired pastor who lived across the street. “But they were so polite. They always looked after you before themselves.”

George was an altar boy looked upon so favorably by the priests that he became a receptionist in the rectory. He also joined a youth education program called the Young Marines, wearing a uniform, marching in step and learning about good citizenship.

“He was very caring toward everyone,” his father said. “Toward anyone who needed anything.”

But George could be a character. In middle school, a black boy named Anthony Woodson stumbled over a chair while walking into a classroom, prompting a student he did not know to joke, “Do you know how to walk, or did you trip over your lip?”