The student discharged a .40-caliber Glock handgun several times while barricaded in the basement of his Willington Street apartment, but never aimed his weapon at police or bystanders, said Chief Inspector Joe Sullivan of the Homeland Security unit.
"He never did anything to indicate that he intended to hurt anyone other than himself," said Sullivan, who led efforts at the scene.
University spokesman Raymond Betzner declined to comment on the incident other than to commend police for their handling of the standoff.
"We're very grateful for what the City of Philadelphia and the police did in bringing the situation to a successful conclusion," he said.
The standoff began after the student's parents filed a police report Sunday, saying their son was suicidal.
When 22d District officers visited the home around 9 a.m., they found the student in the basement with the handgun, Sullivan said.
To avoid a confrontation, the officers went upstairs, he said.
The student fired his weapon during this encounter, Sullivan said, though it was unclear whether he did so intentionally.
SWAT officers and negotiators from the Homeland Security unit quickly cordoned off the street - blocking a basement window with an armored car - and began talking with the student from the top of the steps.
During the afternoon, the student fired again.
"He discharged his gun several more times when he became angry at negotiators, but he was never firing at police," Sullivan said.
Robots and fiber-optic cameras were used to keep track of the student in the basement.
"We used every piece of technology available to us and every verbal negotiating tactic to prevent him from hurting himself, or from forcing our hand to hurt him," Sullivan said.
The student did not have a license to carry a gun and told police that he had stolen the Glock from a friend, Sullivan said. Police were still tracking the ownership of the gun, Sullivan said.
Throughout the ordeal, the student's parents and a roommate were in a Temple police van nearby and were in communication with him and negotiators. They believed their son had stopped taking prescribed medication, Sullivan said.
"He was emotionally unstable and very paranoid about police," Sullivan said.
The student's only demand, was that "everyone leave," Sullivan said.
Negotiators assured him that he would be going to a hospital and not jail, and that if he just came upstairs, he would be able to see his family.
Finally, around 2:15 a.m. Monday, negotiators persuaded the student to put his weapon down.
Looking up the basement steps, the student hesitated, seeming frightened at the sight of a SWAT officer's protective shield.
The officer laid down the shield, and the student walked up the final few steps.