You're wrong. I live in Boston. The MBTA was shut down, but businesses were allowed to open (my employer was), and people weren't getting "swarmed" by any means.
That sounds very different from "not allowed to open".
Police chief saying: "We're asking everyone to shelter in place, no vehicle traffic is going to be allowed to travel in or out of Watertown, until further notice, no businesses are going to be allowed to be opened."
There was coverage of a few incidents of bystanders in cars or taxis being swarmed by cops but I haven't been able to google up any specific reporting on those incidents at the moment. Without trawling through all the live coverage it might be hard to track down.