His family knew he would have called. He always called. Justin Zemser’s life was defined by discipline — the kind that made him his high school’s valedictorian, earned him a place at the U.S. Naval Academy and fueled his ambition to become an elite Navy SEAL.

On Tuesday night, the 20-year-old midshipman had boarded Amtrak Train 188 on his way home to Rockaway Beach, N.Y. When his family learned that the train had derailed — and yet, he still hadn’t called to tell them he was okay — they panicked. His uncle phoned hospitals over and over. He contacted police and the Naval Academy, then more hospitals.

Those frantic efforts ended Wednesday morning when the family learned that Zemser was among the seven who had died. At least one person is still missing, and the names of three others killed in the wreck remained unknown late Wednesday night.

For riders on Amtrak Train 188, the world turned up side down in a flash

But the lives of the four confirmed victims reveal the depths of Tuesday night’s catastrophe: Zemser, the sophomore who was the first in his immediate family to attend college; Rachel Jacobs, 39, the chief executive of an education technology company and a mother who had a passion to help aspiring entrepreneurs; Jim Gaines, 48, an Associated Press software architect and father of two who was known for his composure, kindness and frequent hugs; and Abid Gilani, 55, a Wells Fargo senior vice president from Rockville, Md., who had two children and previously worked for Marriott International.

Still unaccounted for is Bob Gildersleeve Jr., 45, vice president of corporate accounts at Ecolab, a Minnesota-based company specializing in water treatment and energy.

In Philadelphia, Bob Gildersleeve Sr. has been waiting since Tuesday night for news of his son, who has two children. He said Wednesday night that he’s expecting the worst.

Seven families, he said, “are home now making funeral arrangements. Seven families. I pray to God I’m not number eight.”

Though Zemser is the youngest of those known to have died, he had already lived a rich, accomplished life.

“This just shouldn’t happen,” said his uncle, Richard Zemser, as he struggled to speak. “This wonderful, wonderful kid.”

At 5-foot-8, he was co-captain of Channel View High School’s football team and, along with valedictorian, became president of student government.

When he would call his uncle, Richard would tease him: “Am I talking to the first Jewish president of the United States?”

Investigators combed the Philadelphia site where a New York-bound Amtrak train derailed after leaving D.C.

They’d laugh, but it wasn’t entirely a joke. What his nephew wanted, he made happen.

That determination led him to the Naval Academy, which has some of the most stringent admissions standards in the nation.

At Annapolis, he played wide receiver on the school’s sprint football team, a varsity sport limited to players who weigh 172 pounds or less. He was curious, too. He loved to read, especially books about history. Small adventures excited him. His uncle would say, “Where are we going to go today?” and they would end up at the American Museum of Natural History, or Coney Island, riding in the front car of the Cyclone.

Zemser had recently taken his first trip to Israel with a Jewish group from the Academy. In a video posted on YouTube, midshipmen are seen joyfully exploring the country, splashing in waterfalls, stepping through ancient stone arches, spreading Dead Sea mud on themselves and singing by firelight.

Zemser had just switched majors from engineering to English. Earlier this month, he wrote a long, thoughtful letter to his uncle in which he explained that a Bible course had opened his “eyes to a spiritual world well beyond anything I have ever experienced. . . . ”

“Where do I go with this?” he asked.

Midshipman: Bible course ‘rekindled my passion for learning’

He had just turned 20 in March, and on his mom’s Facebook page — rife with photos of her boy — she wished for him to fulfill all of his dreams. He visited her on Mother’s Day, and she posted a message addressed to her own mom, who is no longer living: “Wish you were here to see how your Grandson has grown up you would [have] been so proud of him.”

Like Zemser, Rachel Jacobs had achieved sweeping success.

The daughter of former Michigan state senator Gilda Jacobs, she graduated from Columbia University’s business school in 2002 and, after moving from one big job to the next, joined McGraw-Hill in 2007.

About two years into her tenure there, Jacobs married Todd Waldman, a consultant. She also launched her own nonprofit called Detroit Nation, a group of more than 7,000 fellow Detroiters who offer free consulting for grass-roots entrepreneurs and artists in the Motor City.

In 2012, she had her first child, according to the Cleveland Jewish News. She and her husband named their son Jacob, whose Hebrew name is Chaim, which means "life."

On her Facebook page, Jacobs posted comical and often family-oriented fare. There’s a photo of her mother with her son and another of three dachshunds wearing sweaters.

“En la Calle de Los Besos en Guanajuato,” she wrote next to an image of her and Waldman kissing in Mexico. “Legend says that if you kiss on the steps, you will have 7 years of happiness.”

Two months ago, Jacobs became CEO at ApprenNet, an education technology firm in Philadelphia. After so many years of being a consultant, director, manager or vice president, Jacobs had earned the top job.

“Rachel was a wonderful mother, daughter, sister, wife and friend,” her family said in a statement. “She was devoted to her family, her community and the pursuit of social justice. We cannot imagine life without her.”

The family of Jim Gaines released a similar statement, saying that he was “more precious to us than we can adequately express.”

Gaines was the person who organized the “Bring Your Kids to Work Day” at his Associated Press office. The one who always asked how his colleagues’ families were doing. The guy who gave hugs instead of handshakes.

“He’d say, ‘Hey, I haven’t seen you for a week,’ and he’d give you a hug and ask how everything was going,” said Paul Caluori, global director of digital services at the AP. “Sometimes, you’d think, ‘Is he just putting me on?’” Caluori continued. “But then you’d talk to other people and it was like, no, this is Jim, this is Jim.”

Following meetings in the AP’s Washington offices, Gaines was returning home to Plainsboro, N.J., where he lived with his wife, Jacqueline; son, Oliver, 16; and daughter, Anushka, 11.

Gaines regularly traveled to Washington for work, said Micah Gelman, who was executive producer of AP’s U.S. video operations in Washington and is now director of video at The Washington Post. Gaines’s responsibilities included making sure all of the AP’s videos could be immediately delivered to and broadcast on the many news outlets that subscribed to the AP feed.

Gelman remembers calling Gaines — who once won the IT department’s Geek of the Month award — at home on Christmas Day in 2006 because the AP’s video feed wasn’t showing up properly on different news outlets, and no one else knew how to fix it.

“We were publishing breaking news, and no one could see it,” Gelman said. “He never got flustered when it was all going to hell. He was always just calm.”

Bob Gildersleeve Sr. won’t yet allow himself to talk of his son in the past tense, as if he’s gone. He said he wants to believe that his boy, who was riding on the first car of the train, somehow hit his head and is sitting in a sports bar somewhere, unaware of who he is — but alive. That’s the fantasy he and his wife have shared.

He hopes that’s true, perhaps most of all for his son’s children, who are 13 and 16.

“My grandchildren are broken-hearted,” he said. “And I’m cried out. I can’t cry no more.”

Joe Heim, Michael S. Rosenwald and Julie Zauzmer contributed to this report.