Joseph C. Vignola Jr. and the Philadelphia high school senior met on Craigslist, the Web site popular for its personal ads, police said.
Vignola, 19, and the 18-year-old woman met in person at least once before they got together at the North American Motor Inn on City Avenue last Wednesday, police said. That night, they had consensual sex in one of the motel rooms.
But something went terribly wrong.
Police say Vignola and the woman had an argument and altercation that led to Vignola slashing her throat with a knife.
He was arrested Friday night and charged Saturday with attempted murder and related offenses, including unlawful restraint and false imprisonment. Vignola, of the 6400 block of Drexel Road in the city's Overbrook Farms section, was not charged with a sex crime.
He has been released after his parents posted 10 percent of his $250,000 bail. His father is Joseph C. Vignola, the former Philadelphia City Controller and City Councilman.
The senior Vignola, who lives in South Philadelphia and was in the news this year as he pondered entering the state senate race in his district, could not be reached for comment.
The victim is recovering at Thomas Jefferson University Hospital after neck surgery, said Capt. John Darby, commanding officer of the Special Victims Unit.
Darby said the woman, despite her wound, was able to call 911, telling the operator that she was losing consciousness from bleeding.
"This girl almost lost her life," Darby said.
Despite initial police reports that the woman was bound with a shirt, Darby said further investigation found no evidence of that.
He said the false imprisonment and unlawful restraint charges stem from Vignola not letting the woman leave the motel room.
Vignola surrendered a knife to police and it is being examined for forensic evidence, Darby said.
"The offender's family was very cooperative, as well as the offender," Darby said.
Investigators were led to Vignola based on information developed from an anonymous tip phoned into police the day after the assault, Darby said.