NEW YORK (AP) _ He was a handsome, brilliant pre-med student. She was a striking chemistry major. They met at New York University, fell in love and planned to marry in July.

Shaleen Wadhwani and Hema Sakhrani seemed the perfect couple to everyone around them - everyone except Chandran Nathan.

Apparently obsessed with Sakhrani and determined not to see her wed, Nathan, a 35-year-old married family friend, gunned down Wadhwani on Wednesday on the eve of the student's 21st birthday, police said.

On Friday, the case took another tragic turn: A distraught Sakhrani leapt to her death from the 16th floor of a Queens apartment house.

The murder-suicide extinguished two lives that burned brightly.

Wadhwani was considered a prodigy on the verge of greatness. He graduated from NYU with honors in economics in October, and was granted a full scholarship to enter the medical school's class of 1997.

''Everyone who knew Shaleen was convinced that he would be one of the future leaders in his profession,'' Dr. Ira Goldberg, an associate professor at Columbia University's College of Physicians and Surgeons, told New York Newsday. Wadhwani worked at the school as a research analyst.

The paths of Wadhwani and Sakhrani, U.S.-born Hindus of Indian descent, crossed at NYU two years ago. In April, they celebrated their engagement with a party at the Long Island home Wadhwani shared with his parents.

''They were very anxious to get married,'' said Wadhwani's brother, Deepak Wadhwani.

Nathan, who worked in the city actuary office for seven years, did not share in the excitement, police said.

The Sri Lanka native was a longtime family friend who watched the girl grow into a striking woman he hoped to make his own. For months, Sakhrani rejected his romantic overtures, and her wedding plans made him snap, police said.

''After learning of her engagement, he decided to shoot Mr. Wadhwani in order to prevent the marriage so he could ultimately pursue Miss Sakhrani,'' said Det. Lt. Frank Guidice, who is investigating the case.

Armed with a high-powered assault rifle, Nathan carried out his plan late Wednesday, investigators said.

He arrived at Wadhwani's home shortly before midnight and rang the doorbell, police said. When Wadhwani opened the door, Nathan opened fire, according to investigators.

Hit in the chest with 11 bullets, Wadhwani fell back and died only minutes before his 21st birthday.

Wadhwani's parents, Narian, 60, and Sunita, 56, were awakened by the gunshot blasts.

Nathan was arrested Thursday on the street near his home. He was arraigned Friday on a charge of second-degree murder. Told of Sakhrani's death, he ''showed absolutely no reaction,'' a law enforcement source said, speaking on condition of anonymity.

Homicide detectives went to the Sakhrani family's apartment early Thursday to tell her about her fiance's death.

''She was upset, crying, obviously very distraught,'' Guidice said. ''She just couldn't seem to accept what happened.''

Friday morning, Sakhrani's mood was no better. Seeing newspaper accounts of Wadhwani's slaying made things even worse, family members told police.

At about 9 a.m., she spoke to her brother briefly, then walked out onto a enclosed porch. There, she slid back a window and, as her mother watched in horror, jumped out.

Her body was found face down on a grassy courtyard 16 floors below.

Among her last words: ''Why did it happen? Why did it happen?''