(Portland, OR)  --  North Carolina-based folk rock group the Avett Brothers are rescheduling their third Troutdale show after a man with a gun reportedly got past security.  The Multnomah County Sheriff's Office says the band was getting ready to perform at the McMenamins Edgefield Saturday night when the incident happened.  Police say a man claiming to be an out-of-state police officer set off a metal detector when entering the venue and then slipped out of sight of the private security contractor working at the event.  The Avett Brothers decided to cancel the concert out of precaution.