William Gwathmey was the first to help strangers carry their groceries down the street or grab an extra chair if someone needed a place to sit. His selflessness was a magnet for friends across campus and family in his hometown of New York City.

“He had a huge heart,” his mother, Rose Harvey, said. “He was always thinking about everyone else.”

The 20-year-old, who was pronounced dead Friday morning, was happy and “full of life,” constantly surrounded by his friends and dozens of cousins, his mother said.

Harvey described her son as a “homebody,” who often came back to his family in New York on the weekends. He had spent just two nights away from home before going to college. In family pictures, Gwathmey was often sitting on his parents’ laps or draping his arms around his older sister’s shoulders, Harvey said.

Gwathmey’s official cause of death has not been determined because a report by the D.C. Chief Medical Examiner’s office is not yet complete. The junior had used cocaine and drank alcohol the night before his death, according to a Metropolitan Police Department report. After going out to several nightclubs that night, Gwathmey returned to an apartment at The Residences at the Ritz-Carlton on 23rd Street, where he was later found unconscious on a couch, according to the report.

His family said that friends studying abroad as far away as Prague have flown back to be with them since Gwathmey’s death, and teammates from his high school basketball team gathered at his home to share stories. Heartfelt posts from friends filled Gwathmey’s Facebook page over the weekend.

Russell Harrison Pershing, Gwathmey’s roommate from freshman year, said Gwathmey helped make the best of a four-person room in Thurston Hall, describing Gwathmey as “extremely helpful and always willing to talk.”

“He had a plethora of friends and I don’t know a single person that had a bad word to say about him,” Pershing said.

Gwathmey was a member of the Alpha Epsilon Pi fraternity and played club basketball.

He decided to study finance and economics after developing a love of economics in high school. He dreamed of working on Wall Street and interned at a small private equity firm last summer, his family said.

Gwathmey was a 2012 graduate of an elite all-male prep school, Collegiate School in New York City. His junior and senior years, he helped his varsity basketball team win back-to-back state championships. He also played varsity tennis and was a member of the Young Republicans.

“He wasn’t the superstar. He was the guy that worked really hard and was happy to back up everybody else. He was the unsung hero,” Harvey said.

His family will hold a memorial service at the Unitarian Church of All Souls at Lexington Avenue and East 80th Street in New York City on Sept. 24.