An 18-year-old man has been arrested in the killing of Sabina Rose O'Donnell, the young waitress who was sexually assaulted, beaten and strangled June 2 while on her way home after a night out, police said.

Donte Johnson, of the 900 block of N. 11th Street, is expected to be charged today with murder, rape and robbery in O'Donnell's death.

Police believe Johnson is the man seen on surveillance footage biking around Northern Liberties and Fishtown for an hour before crossing paths with O'Donnell and following her home to her apartment near North 4th Street and Girard Avenue.

The killing began as a robbery attempt that escalated quickly, Captain James Clark said today. Johnson, Clark said, started out wanting to steal O'Donnell's bike.

An anonymous tip on June 11 led police to start searching for Johnson, who was already known to police in the area. When two officers spotted him days later, Johnson fled.

On Tuesday, Johnson's mother called police and arranged to have her son turn himself in. He surrendered to police around 8:30 p.m. Tuesday, surrounded by family members.

Police sources said Johnson has already confessed, but Clark would not comment on that.

"I will say we're 100 percent positive we have the right person," he said.

O'Donnell, 20, was out with friends in Northern Liberties from 7:30 to 10:30 p.m. June 1, then went to a friend's apartment at Front Street and Girard. Police believe she left between 2 and 2:30 a.m. June 2, and biked home.

Johnson, meanwhile, was biking around the neighborhood, on the prowl for someone he could rob, Clark said.

According to the video footage, O'Donnell crossed paths with Johnson around 2:48 a.m. Police believe O'Donnell reached the front of her apartment building, where Johnson caught up with her.

"He went to take her bike, she screamed, maybe gave a slight struggle," Clark said.

Johnson dragged her behind the building, attacked her and left her there. After the killing, Johnson tried to break into apartments in O'Donnell's building, police said, but ran away when a neighbor saw him.

A passerby found O'Donnell's nude body shortly before 10 a.m. the next day.

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