FRIDLEY, Minn. - Mike Briggs is trying to continue business as usual at Minnesota Firearms butit's difficult after your shop gets broken into three times in 15 months.

The latest break-in happened on Monday.

"Somebody smashed the front window using a boulder the size of bowling ball and made entry through these bars," Briggs said.

The thief went to the back, shattered the glass counter and got away with 8 handguns.

"We have increased security around here substantially and it's unbelievable to me that they keep doing this," he said.

Last year thieves broke through the front door taking several firearms and just this July thieves broke in again and stole 23 guns.

That same month thieves also hit DKMags in New Brighton.

"They did a lot of damage to the building and got away with firearms," shop owner David Korbin said.

Korbin said nine guns were stolen. He's beefed up security and hasn't had an incident since. However break-ins at other shops has Korbin on guard.

"I just contacted every gun shop owner that I know of. Told them what happened and how it happened so they can prepare for it and minimize their losses," he said.

The Bureau of Alcohol, Tobacco, Firearms and Explosives, or ATF, said stolen guns often end up as crime guns. Last year more than 2,000 guns were recovered and traced in Minnesota, the majority of them in the Twin Cities, according to an ATF report.

Briggs said next time thieves try to break in they'll be greeted by new ear piercing alarms and high end surveillance cameras.

He is offering a $5,000 reward for information leading to a conviction.

The ATF is asking anyone with information about this case and other missing gun cases to call their St. Paul office at (651) 726-0230.