Boston's Beth Israel Deaconess Medical Center held its largest-ever training drill Wednesday, involving hundreds of hospital staff members and dozens of actors. The mass casualty drill mimicked a mass shooting at a fictitious nearby college. It lasted 90 minutes and involved nine departments from across the hospital's Longwood area campus.

During the drill, staff set up triage locations, practiced identifying unconscious patients, and set up a staged family waiting area where relatives could go to be reunited with loved ones.

Meg Femino, senior director with Beth Israel's emergency management department, said the goal of the exercise was to be as realistic as possible.

"We realize that we're a major academic medical center, we're located a couple of blocks down the street from Fenway Park and we have six colleges around us. So, we think it's important to be able to service the community and that we're prepared for events that impact us," she said.

Femino added that this type of drill is invaluable for training staffers, as it helps to improve staff members' "muscle memory" and identify weaknesses. But it takes a lot of planning.

"The really big scoping exercises like these, we'll do every couple of years, because it's an enormous project to pull something like this off," she said.

The hospital conducts smaller drills on a regular basis throughout the year — they conducted 19 of these in 2018.