The South Boston convention center will only seem to be under siege tomorrow

The Massachusetts Convention Center Authority alerts us that if you see lots of cops and EMTs swarming the Massachusetts Convention and Exposition Center tomorrow, remain calm: It's just a training exercise for dealing with an active-shooter incident.

The authority says that between 9 a.m. and 3 p.m., you can expect to see a lot of cops and other emergency responders in and around the convention center.

The authority says the run-through, dubbed Operation Vanguard, is the culmination of two years of planning by local, state and federal authorities to create an "Active Shooter Joint Response Plan" should some horrible incident actually occur within New England's largest convention center.

The live exercise will bring together the full complement of expertise, resources and personnel of the respective agencies to test critical elements of the plan and validate the unique protocols developed to implement a full-scale response to an emergency situation at the BCEC.