PORT JEFFERSON, N.Y. (CBSNewYork) — Family and fraternity members are searching on foot for a 23-year-old college student whose body is still missing after a plane crash on Long Island last weekend.

Four people were on board the Piper PA 28 aircraft as part of a birthday celebration when it made a forced landing less than one mile offshore around 11 p.m. on Feb.20. Three people were rescued, but Gerson Salmon-Negron, 23, was not found.

Suffolk County Police said in a statement that student pilot Austricio Ramirez, 25, was flying the plane when it began experiencing difficulties and turned over the controls to instructor pilot Nelson Gomez, 36.

Gomez landed the plane in the harbor and all four people on board were able to exit the plane. Ramirez, Gomez, and Wady Perez, 25, were rescued by Suffolk County police. 

Negron’s mother was heartbroken and crying as she walked near the water in Port Jefferson Saturday, searching for the remains of her son, WCBS 880’s Sophia Hall reported.

“He was my life and I don’t understand why this happened,” she said. “How come the three others are alive, and my son is nowhere to be found?”

Coast Guard officials said the initial search for Salmon-Negron went on for 18 hours through the night, covering 90 square miles before the agency pulled its personnel from the search. Two police department boats and a dive team continued searching the harbor Sunday afternoon.

About 40 family friends and fraternity members were out walking in the chilly weather for the hours-long search. Members of the Suffolk County Police Department also joined in for assistance.