Probably at first, while it is all new to folks. Marijuana stores are very mellow places by nature. As for patrolling cops, they don't even look when they drive past marijuana shops.
Fall River is a nasty city.
One of the towns/cities which were the beginning of the Industrial Revolution, the former mill town has suffered economically since the Civil War.
It is a highly depressed area and there is a lot of crime.
The security is to prevent the store from being robbed.
I was mugged, robbed of thousands of dollars, had my car destroyed and was physically assaulted in one bad incident in Fall River, almost 40 years ago. It hasn't gotten better.