PHILADELPHIA -- Third-year medical student Lea Sullivan walked out of a grocery store Sunday afternoon onto a busy sidewalk in one of the city's most vibrant neighborhoods, and met a savage, inexplicable end.
A burly man in a ski mask attacked the former homecoming queen from behind, clubbing her in the head with a baseball bat and continuing to beat her after she fell. The attack lasted seconds -- a minute, tops. Although South Street was crowded with shoppers, no one tried to stop the attack.
But witnesses did get a good look at the assailant, who removed his mask. ''He took it off so everybody could see him," said Lieutenant Michael Morrin of the homicide division.
Bystanders also took down the man's license plate number, leading police to Nader Ali, 26, a former medical student who had been placed on leave from Jefferson Medical College last year because he had been acting erratically, according to a school spokesman. Ali was arrested Monday at his parents' home in New Jersey.
Police have not disclosed a motive for the attack and refused to comment on Ali's mental state or provide any other details, other than to say that Sullivan's roommates described Ali as just an acquaintance of hers.
The slaying shocked and baffled friends and classmates at Jefferson and cast the campus into mourning.
''What a beautiful girl," said Miriam Massucci, who works at a flower shop across the street and saw Sullivan being loaded into an ambulance. ''She could have found the cure for something, and now she's gone."
Sullivan, who was from the well-to-do suburban Philadelphia community of Bryn Mawr, died Monday at Thomas Jefferson University Hospital, where she and her classmates made rounds as part of their third-year duties. A Harvard University graduate who played lacrosse, soccer, and track at Radnor High School, Sullivan lived with roommates a few blocks from where she was beaten.
Friends and fellow students described her as friendly, popular, pretty, athletic, and outgoing but offered little other information about her, saying Sullivan's family had asked them not to talk. Her parents did not return a call, nor did Ali's.
On the Jefferson campus, students consoled one another. A shrine of candles and flowers marked the spot where she was killed, while a detective canvassed the neighborhood for witnesses.
A Jefferson spokesman, Jeffrey Baxt, said Ali was a second-year med student when he was placed on medical leave because of ''an extreme change in behavior." Baxt would not elaborate.
In 1998, Ali, then 19, was charged with assault and serving alcohol to minors following a brawl at a friend's house, The Record of Hackensack, N.J., reported at the time. Ali, trying to get unwanted guests to leave the party, started the fight by throwing a cigarette in a guest's face, police said. He was hit in the head with a bottle and needed 30 stitches. It was not clear Tuesday whether Ali was convicted in that case.
At a court appearance yesterday in New Jersey, Ali refused to sign a waiver allowing him to be returned quickly to Pennsylvania to face a murder charge, prosecutor James V. Santulli said. An extradition hearing was scheduled for early December.