A gun inside a flight attendant's handbag accidentally discharged just after 6:30 a.m. Sunday at Philadelphia International Airport.
The flight attendant is an employee of Republic Airlines, which operates the US Airways Express flights out of Philadelphia, said airline spokeswoman Liz Landau.
The flight attendant put her handbag on the X-ray machine conveyor belt as she went through the routine security check.
TSA officers noticed the gun and alerted a Philadelphia police officer, TSA spokesman Jim Fotenos said.
City police, who are handling the investigation, were not immediately available to explain how the gun went off.