Ensign Watson was shot five times. He managed to crawl out of the classroom building, Ms. Watson said, and gave emergency personnel a description of the gunman and his location, “and then he collapsed.”

She recalled her son telling his parents from the time he was in the United States Naval Academy about how he would respond if he was faced with an active shooter: “He told us, ‘Mom, Dad, if I’m ever confronted with them, you know I’m going in full force.’ And that’s what he did.”

Ensign Watson, whose given name was Joshua but who went by his middle name, Kaleb, was the youngest of three brothers. He first wanted to be a Marine, like one of his uncles, and later a Navy SEAL, his mother said. He ultimately decided to become a pilot, so he could have a military career and later perhaps a civilian career as well.

He was a skilled marksman, captain of his high school rifle team in Enterprise, Ala., and later at the Naval Academy in Annapolis, Md. He moved to Pensacola two weeks ago to begin flight training.

He had purchased a five-bedroom home — along with a leather sectional sofa, a lawn mower and weed trimmer, his mother said — and was looking forward to renting rooms in it to other aviation students and to living only a couple of hours’ drive away from his parents.

The family spent Thanksgiving together, and Ensign Watson and his father, Benjamin Watson, both Auburn fans, watched the Iron Bowl. Then, for the first time in the five years since he left for the Naval Academy, the young man helped cut down a Christmas tree and decorate it.

“He was the one that put the angel on top,” Ms. Watson said. “And it’s still there.”

Airman Haitham’s family moved to St. Petersburg, Fla., from New Orleans after Hurricane Katrina. The airman, who went by “Mo,” was home in St. Petersburg the day after Thanksgiving to watch his younger brother play high school football. Susan Alvaro, an assistant principal at Lakewood High School, where Airman Haitham graduated last year, said he gave her a big hug when he saw her at the game.