At one Washington Mutual branch in Los Angeles, the suspects stole customer account information when a customer swiped his or her card.
Surveillance video showed the man attaching the skimmer on the access door. Normally that skimmer is used to allow customers access to an ATM, however, what the man installed also allowed him to access account information.
"Once the consumers have left, they would then remove the device that has captured the account numbers, take those account numbers, take a normal piece of plastic or a credit card, [and] enter those numbers onto that credit card," said Detective Robert Zaun, Glendale Police Department.
Police arrested three people in this case: Meher Abolian, Tiffany Conant and Rane Melkom. Detectives believe they may be involved in more crimes at other banks. The suspects allegedly had electronic equipment, including wireless video cameras.
"The crooks would also take a pamphlet holder, a leaf holder ... And they would mount it next to the PIN display, and as the consumer would type in his PIN number, the hidden camera would capture those numbers," said Detective Zaun.
ATM customers said they've heard of scams, but they are surprised at how sophisticated a crook can be.
"It's scary," said Gat Fama, a bank customer. "It's really scary because they're stealing people's money."
ATM fraud affects 3 million people a year and it costs nearly $3 billion to cover.
Authorities say people need to be aware and look around the ATM to make sure nothing looks unusual.
"I didn't even know about that. So, that's good for me to know, so I can be safe," said Brett Lemos, another bank customer.
Police say this is an ongoing investigation and that they are working with other police departments to see if the suspects had committed crimes at other locations.