Prosecutors said the trio broke in, smashed the display cases and packed up more than 35 guns, mostly handguns and rifles.
The trio ran into problems when they tried to leave.
“The thieves apparently had trouble getting their loot out of the store, and at one point, one suspect fired shots through the shop’s front door in an effort to get out,” prosecutors said.
Marietta officers shot back, but no one was hit.
The standoff occurred days after the deadly police shootings in Dallas and Baton Rouge.
"We had to be careful because it's a gun store and police are being shot at these days," Marietta police's Brittany Wallace told Channel 2 Action News at the time. "There is a fear right now in law enforcement. People seem to hate us."
Cobb superior court judge Mary Staley Clark also sentenced each of the men to 10 years probation.
“This was a very dangerous crime that held potentially catastrophic repercussions had those weapons made their way to the street and the hands of other criminals,” said the case’s prosecutor Jaret Usher.
It happened at the Deer Creek Gun Store on South Fairground Street Tuesday morning.