The Community College of Philadelphia was on lockdown for about 45 minutes Tuesday morning after a report that a man entered a building with a gun, police officials said.
But police say that, after investigating the situation and interviewing witnesses this afternoon, they are unsure whether a gun was ever brought onto campus.
"There is some question as to what took place. We're still investigating it," said Commissioner Charles H. Ramsey. "We have no gun, and we don't know if there was, in fact, a gun. We've still got a lot of work to do."
A 19-year-old student initially told police that he had fought with a 17-year-old student, and the 17-year-old flashed a gun at him, Ramsey said.
The college went into lockdown, and police and SWAT teams swarmed the campus, searching for a potential gunman, as news helicopters hovered overhead.
But after the fight, 17-year-old calmly walked to a class building and sat down in class, Ramsey said.
"He didn't seem to be rushing or doing anything unusual at all," Ramsey said.
When the lockdown was announced, the boy left the campus with the rest of his classmates.
He was brought into custody after police learned his name, but police have not found a gun on campus or with the student, Ramsey said.
The boy told police that he had fought with his 19-year-old accuser, but never brought a gun to campus. He characterized the altercation as "somewhat minor," Ramsey said.
The accuser's story "is starting to not match up," Ramsey said. He said the older teen had initially told police he had caught only a glimpse of a gun. Later, he told investigators he could identify the make and caliber of the gun, Ramsey said.
In addition, another witness told police she had watched the entire encounter between the teens, and had not seen a gun at all.
Students and staff were told to stay in their classrooms and offices as police searched. Philadelphia police then tweeted that there was no active shooter and described the incident as a "personal dispute."
The suspect was taken into custody by 11:45 a.m., police reported.
Masterman, a magnet school for high school and junior high school students located across Spring Garden Street, was also placed on lockdown, according to Fernando Gaillard, a school district spokesman.
The scare came one day after colleges around the region stepped up security, prompted by an anonymous Internet threat of a mass shooting at a school near Philadelphia. There were no incidents.
The community college closed early for the day. It will resume its normal schedule on Wednesday.