Yesterday I heard a bunch of sirens and a bit later saw the channel 7 news helicopter, but I couldn't figure out why. This morning I found the explanation.
Around 4pm on Friday the Bank of America at 7316 Wisconsin Avenue, Bethesda, MD was robbed by someone with pepper spray. This robbery has a happy ending though, customers and bank employees chased the robber down the street and apprehended him. More info from WJLA.
This is the third (and hopefully last) bank robbery I have heard of in Bethesda in the past couple of months.