HEWLETT, New York -- Richard Zemser described the feeling of "what-if." What if his nephew had been late to the gate, or in a car to the back of the train, or if things had played out differently. "Just thinking about that moving train is unconscionable," he said.

Family and friends of Justin Zemser, a U.S. Naval Academy midshipman, gathered to share stories of his life and death Friday in Hewlett, New York. The memorial service was the first funeral to be held for one of the eight victims of the Amtrak crash in Philadelphia Tuesday night that also left dozens more injured. 

During the service at Boulevard-Riverside-Hewlett Chapel on Long Island, Zemser's short 20 years of life was honored by loved ones to a room full of bowed heads  -- midshipmen in somber dress whites, old high school friends, football teammates and synagogue members in standing-room-only pews. Speakers took to a lectern rising above a casket draped in an American flag.

Zemser's father, Howie Zemser, said everyone there had "some sort of story about Justin." "Son, you will be missed by all of your friends, but mostly you will be missed by your mother and your father," Howie Zemser said. "Son, you gave me such strength. You will be in our hearts and thoughts forever."

Michael Citelli, a football teammate of Zemser's from high school, said his life was changed by their relationship. "Because of everything that he's done, I'm going to learn to better myself," he said, and that he would "be a different person than I was just a few days ago."

The derailment in Philadelphia came as the Amtrak train was going more than 100 miles per hour in a 50 mph zone. Investigators are looking into why the train was speeding.

Zemser was an only child to his parents Howard and Susan. In high school he was a football player at Channel View School for Research in Rockaway Park, then went on to the Naval Academy in Annapolis, Maryland. He was a sophomore when he died. 

Mitchell Bond, Zemser's roommate at Annapolis, described Zemser's dual nature while choking up. He was "physically an animal," and "mentally a genius," Bond said to laughter. Zemser was also remembered as an avid reader, a good book his relaxation. 

The Zemser family's Jewish faith was a central theme of the memorial service and was cited as a strength during this difficult time. Zemser himself had recently taken his first trip to Israel. He hadn't even had the chance to share all of the details with loved ones yet. Marine Corps Capt. Brandy Soublet, Zemser's company officer, said the midshipman told her repeatedly that the experience was life-changing. "Howard and Susan, you raised the most amazing man," Soublet said. "He was a light in our company. ... He absolutely created a void in our hearts."

His father described his son's good deeds -- like helping cleanups after Hurricane Sandy and volunteering at soup kitchens -- and shared family moments. There was young Justin playing in the park on monkey bars or setting up pretend store-counters.

"I taught Justin how to play chess," said his father. "In the beginning, I beat him. That didn't last very long."

Howie Zemser also shared the story of how he and his son had tried to fly a box kite when Justin was young. But the experience was frustrating and his father had recently bought a new kite that they had planned to fly together again. Now that will never happen.