( CNN ) -- Hours after being released from jail , a man walked through an emergency door at San Diego International Airport , onto the tarmac and sat down on a United Express plane Tuesday , according to San Diego authorities . `` He completely bypassed TSA screening , '' San Diego Harbor Police Chief John Bolduc said . `` He was in a public area and went out an emergency fire door , which gave him access to the tarmac . '' Marc Duncan , 38 , was paroled from jail Monday night , according to San Diego County Sheriff 's Department records . He had been serving time for theft . After it was opened , the emergency door alarm sounded , and Bolduc said police were on site in four minutes , but by then Duncan had blended in with other passengers . He allegedly boarded a 30-seat United Express aircraft operated by SkyWest , which was heading to Los Angeles , according to airline spokesman Wes Horrocks . The flight attendant realized she had too many passengers , Nicholas Blasgen , a passenger on the plane told CNN affiliate KGTV . `` They said , 'What is your count ? ' She said this is my count , and they said that is wrong . '' The passengers got off the plane and their luggage was searched . `` They had us put all the bags out , they separated the bags by enough distance and had the dog go over everything , '' Blasgen said . Duncan was identified and arrested . He is being held in the San Diego jail and is scheduled to be in court Thursday . `` I still ca n't , in the world , understand how this happened , '' Blasgen said . `` It sounds like they just have lax security or not enough management . Something was going wrong . '' The Harbor Police chief said they will examine this incident and find out where to make security improvements . `` The guy did breach security , but he was caught , '' Bolduc said . `` We have multiple layers of security built into our airports , as you know , and the backup systems were able to catch this guy . '' `` Security of airports is a shared responsibility , and airports and airlines are required to adhere to TSA-approved security standards . '' TSA spokeswoman Sterling Payne said in a statement . `` TSA has initiated an investigation and if necessary , will take appropriate action . '' CNN 's Todd Sperry contributed to this report .
Hours after leaving jail , man boards plane with no ticket . Comment: Passenger says everyone left the plane , bags were searched before man was found .