Police seized two illegal firearms at last month's Saxet Gun Show at the Travis County Expo Center.
They say a 19-year-old convicted felon was arrested at his home Tuesday.
Police have asked FOX 7 not to identity the suspect because of an ongoing investigation. They say the 19-year-old and three others brought two firearms to the gun show December 15.
They are a Merkel 12 gauge shotgun and a Savage model Stevens 200 rifle.
Three off duty Austin police officers working security say they noticed the four men right away. The group didn't know much about the firearms and was acting nervous.
"Most people that are gun owners know the make and model of the shotguns and know the value of the shotguns," said Detective Pat Wines with the Austin Police Department's Gun Unit.
After the group sold one of the guns, one of the officers ran the serial number, and discovered it was stolen.
He says selling illegal guns at a gun show is not hard.
"You just have to find the person who wants to give the money and not do the background check," Wines.
Detective Wines says proactive measures like this is what they would like to do but can't. Right now, his unit is swamped with illegal gun cases, many are federal and time consuming.
He says they are reactive to crime rather than proactive, waiting for crime to happen before responding. Police would like for that to change, especially with the upcoming Saxet Gun Show this weekend.
Detective Wines says he has no doubt they would uncover illegal activity there.
"If we had the resources, undoubtedly we would find other weapons that maybe stolen and other prohibitive persons from possessing firearms being convicted felons or otherwise prohibitive," he said. "It's because gun show allows traders and people who are not dealers to trade guns with one another without doing any paperwork or to sell guns amongst each other without doing paperwork."
The Austin Health and Human Services Committee discussed ways to expand gun control and safety last week.
Councilman Mike Martinez said its part of a national conversation.
On Tuesday, Chief Art Acevedo said APD is working on a plan to reduce the city's gun violence.
The 19-year-old suspect is charged with unlawful possession of a firearm by a felon. If convicted, he could face up to 10 years in prison.