Witnesses say a man started yelling and acting erratically as movie previews were wrapping up, just before 8 p.m.
When the moviegoers confronted him, they said he pulled a gun on them.
People in the theater ran out but the man reportedly calmly stayed in his seat.
The SWAT team evacuated the entire Metreon as a precaution.
Officers detained the man and found a handgun on him.
Nobody was injured.