Stranger Too Close At Post Falls ATM

Moments ago, the police scanner reported that a strange guy from a Jeep Cherokee was walking up to Post Falls Bank of America customers using the ATM, carrying a black box. One customer ordered the guy to back away. Dunno about you, but I feel awkward standing in line at an ATM because it’s hard to tell how far to stand behind the person using the machine. At my bank, I stand back about 10 to 12 feet because the bank doors divide the space. So here’s the question …

Question: How much distance should those waiting in line give the user of an ATM machine?