At the Northern Liberties park that Sabina Rose O'Donnell treasured, mourners arrived early today to celebrate her life.

Nearly 100 people had gathered before 3 p.m. for a memorial service at Liberty Lands where the slain waitress once hung out with friends, walked dogs, and played with ladybugs.

Hundreds more were expected this afternoon to flock to the park at Third and Poplar Streets to raise glasses of champagne in a toast to O'Donnell, 20, who was murdered last week outside her apartment building.

Talea Bella, 28, of Old City, was the first of many performers who took the stage in the park to honor O'Donnell, an aspiring dancer.

Bella said she became choked up as she sang an a capella rendition of "Something Out There," a ballad from the 1987 movie An American Tale.

"Nobody could have thought something like this could have happened to such an innocent, sweet, and uncorrupted girl," said Bella, shortly after the "Everybody wanted to be friends with her."

As a DJ played upbeat club music, the park began to teem with friends, family and neighbors who brought potted flowers and single-stemmed roses.

Under four white festival tents, volunteers scurried to prepare food and drink from some of O'Donnell's favorite neighborhood restaurants.

Ashley Keller, 24, a manager of the El Camino Real in Northern Liberties, said she had never met O'Donnell.

"It's a time for Philly to come together for the same cause," Keller said. "It's not necessary if you knew her or not. But together as a customer service workers we're a close knit family."

The memorial was scheduled to run until 7 p.m.

No arrests have been made in the killing of O'Donnell, who was strangled early last Wednesday after leaving a friend's apartment and biking home a few blocks. Police believe she was killed by a stranger who approached her in front of her home on Fourth Street and Girard Avenue, then dragged her behind the building. Her body was found the next morning.

Police have been analyzing DNA evidence as well as a T-shirt that may have been worn by O'Donnell's attacker.

Investigators today released surveillance video of a "person of interest" seen following O'Donnell shortly before her death.

The footage, captured by several security cameras around Northern Liberties and Fishtown, shows a cyclist biking around the neighborhood for almost an hour. At one point, O'Donnell can be seen biking past him, pedaling in the opposite direction down 4th Street near Girard Avenue, and the man turns his bike around to follow her.