School Police Sgt. Tyisha Wright-Godwin approached the male - not a South Philadelphia student - and he told her he was waiting for a friend.
Then "it got really scary," principal Otis Hackney said.
Almost immediately, a bulletin came across the officers' radios: the young male had threatened a South Philadelphia student. Then, the officer monitoring school security cameras radioed that he saw the young male pass what appeared to be a gun to a student, who put it in her bag.
School police officers are not armed, but Wright-Godwin was single-minded, Dorsey said.
"She knew she had to get that gun," said Dorsey.
A struggle ensued - Wright-Godwin trying to grab the bag, the male trying to grab it back. Ultimately, the young male fled and two other school officers joined Wright-Godwin, taking the girl into custody.
Everything was over in minutes.
"Other students didn't gather around. They had no idea what was going on. The officers just swooped right in and took care of it," Hackney said.
Wright-Godwin is a South Philadelphia graduate, and invested in the community. She took it personally that someone would bring a gun to "her" school, the principal said.
"She cares about South Philly, even the knuckleheads," Hackney said. "She wants them all to do well, and she makes sure that everyone's on point."
The .38-caliber Smith & Wesson was loaded with five rounds of ammunition, and its serial number had been altered, Dorsey said.
The girl, whose name is not being released because she is 16, had a prior record and was charged with possession of a firearm and resisting arrest, Dorsey said.
The young male is still at large.
Contact Kristen Graham at 215-854-5146, firstname.lastname@example.org or on Twitter @newskag. Read her blog, "Philly School Files," at www.philly.com/schoolfiles.