By Mark Abrams

PHILADELPHIA (CBS) - Philadelphia police say a Germantown High School freshman surrendered Tuesday in the company of his family to face charges he sexually assaulted a female classmate last week.

Special Victims Unit Captain John Darby says police were called by school officials late Friday morning after the victim broke down in her first class and told a teacher of the alleged assault which she said happened at the bottom of a stairwell in the school’s basement.

Darby says investigators recovered evidence and quickly reached their conclusions.

“I can tell you that what we do have is compelling, and, again, as I said, as I indicated, the investigation proceeded immediately, it was aggressive to the point where a probable cause, our investigators felt probable cause was met by day’s end on Friday.”

Darby says the teen-age victim told police she had only known her alleged attacker for a few weeks.

Police say the teen-age boy accused in the rape is facing a long list of very serious charges.