Boeing says an employee didn't properly check the machine gun through security. When he passed through a turn style and went into the building with the weapon, several employees called police to be safe.
Swat officers evacuated the building. Officers quickly found the man and the mock weapon.
He was not charged.
Boeing says the gun was to be part of a display.
Police say they were told that supervisors at Boeing would hold a meeting Tuesday to adjust policy regarding future training exercises.
