CHARLOTTE, N.C. -- According to police, thieves ripped opened the wall of a discount store, only to fail to crack the safe. Police said the thieves are the same that have hit Family Dollar and Dollar General Stores in Charlotte, Stallings, Marshville, Monroe and Concord.

The thieves who hit a Family Dollar Store on Sunset Road left the safe behind, but still did plenty of damage breaking down a concrete wall.

Miles away from north Charlotte, the case struck a chord.

"I said, 'That's our guys. They're back at it,'" said Stallings Assistant Police Chief David Hearn.

Hearn said a Dollar General Store was hit there just a few weeks ago. Crime scene photos from that case show almost identical damage to Monday's break-in.

"They know the inner workings of the place, they know that it's closed, they know surveillance, they've done their homework," said Hearn.

He said in the past year, four Union County discount stores were ripped off in the same way.

Concord police have seen five cases, too, where someone used heavy equipment to break through concrete walls of a business.

"The MO is too close to ours. The guys are hitting the same kind of store over and over, taking the same type of product with the safe, etc," said Hearn.

It's disconcerting to shoppers who worry about the kind of criminal who's responsible.

"Yeah, that's pretty bold and it seems like it would take time, too. But late at night or early in the morning, I guess there's nobody around," said shopper Johnny Hicks.

Police said they have some leads and hope to close the case before another business is hit.

Charlotte-Mecklenburg police crime stats for the university area show burglaries are up year to year. Last year at this time, there were 100 commercial burglaries in that area. This year there are 140 from January to the end of June. That's a 40 percent increase.