(Image Credit: ABC News)

The holiday season isn't here yet, but a group of real-life grinches has already caused trouble at two Pennsylvania Walmart stores.

Police say the group of thieves, which they believe consists of three men and one woman, have stolen from Walmart trailers holding presents, such as bikes and electronics, that have been put on layaway.

"It's just devastating, people have been through so much, and now they're hitting them before Christmas? It's terrible," shopper Sandra Schmidt told ABC News affiliate WNEP.

Walmart began offering layaway plans to customers on Sept. 16, a month earlier than last year, to "give families an extra month to shop and stretch their paychecks further this holiday season," a statement on the retailer's website said.

The thieves, who police believe are in their teens or early 20s, were captured on surveillance video walking out of a Taylor, Pa., Walmart without paying for the same tools they would later use to break into trailers where layaway gifts are held for customers.

Between the store in Taylor and another heist in Dickson City, the thieves have managed to get away with thousands of dollars worth of merchandise, police say.

In a statement, Walmart vowed to stand by their customers.

"It's really sad someone would steal gifts for the holidays," a spokesperson told ABC News. "At the end of the day, we will do what is right for the customer."