Penn State Abington was on a brief lockdown Thursday afternoon after witnesses reported seeing a man with a shotgun on campus.
The weapon turned out to be a BB gun, police said.
"The person who actually brought the fake gun onto the campus had gone home already, but saw the stir he caused, so he called in to the police and said who he was," Abington Police Chief Bill Kelly told reporters.
Police picked up the gun, the man, and two other people. It was unclear Thursday whether they would face charges.
The lockdown was announced about 4 p.m., when the campus emergency-alert system told students and staff to "shelter in place." It was lifted just before 5 p.m.
No one was ever in danger, the university reported, and normal operations resumed immediately.