ORONO, Maine — University of Maine nursing students and EMTs prepared for the worst during a training exercise on Friday, making tough calls about who would live and who would die in the wake of a mock mass shooting on campus.

Around 10:15 a.m., seven shots rang out inside the UMaine Field House. A police officer posing as a shooter at a sporting event fired the blank rounds before being neutralized by another officer.

About 30 participants, mostly nursing students and instructors, dropped to the floor and took cover, faking injuries, crying for help or lying motionless and quiet in a pool of fake blood. Some wore makeup simulating injuries, blood spatter or pale complexions.

“This is an unfortunate possibility in nursing that isn’t often covered in the classroom,” said Kelley Strout, an assistant professor in the nursing program who helped organize the drill. “We want to ensure our future nurses are prepared for anything as they go on to their careers.”

A few minutes later, EMTs from the University Volunteer Ambulance Corps arrived and shouted that anyone who could hear them and walk should head for the exits. All but a few victims stayed on the ground, and EMTs made their way around the room, assessing the condition of each patient. An instructor pretending to be a panicked witness ran around shouting, trying to pull EMTs and stretchers toward certain victims and generally interfering.

The medics triaged patients, assigning each a colored tag based on their condition. Red patients needed urgent life-saving care, yellow for those with serious injuries that aren’t believed to be life threatening, and green for “walking wounded” with minor injuries, and patients with black tags were either dead or expected to die.

In all, 20 mock shooting victims were transported by EMTs to a mock hospital set up in Dunn Hall, home to UMaine’s nursing program. About 40 student nurses, seniors in the program, awaited their arrival outside. Some came in ambulances, while those with lesser injuries piled into a car that brought them to the hospital.

Once victims began to arrive, the nurses got a taste of the confusion that can result from a mass casualty incident like this.

Nursing seniors Linnea Barnard, 24, and Natalie Bolduc, 21, treated an infant — a doll — who arrived with an incorrect triage tag, resulting in confusion and frustration for the nurses who were trying to treat the baby.

“It proved that communication is so important in a disaster,” Bolduc said.

Each patient came with a card that indicated changes in their condition, such as a drop in blood pressure during the ambulance ride or a sudden recovery of consciousness. When the infant’s condition worsened expectedly, in part because of the error in triage, Bolduc and Barnard had to make the difficult decision to move on to other patients that they could help.

“This is way different from what we’re trained on in the classroom and in typical hospital settings,” Barnard said. “You have to save as many people as you can with the limited time and resources you have.”

EMTs from Orono and Old Town assisted, overseeing the students’ work, offering advice, and driving ambulances from the disaster scene to the mock hospital. In the mock hospital, nurses from area hospitals assessed and critiqued how the nurses dealt with each patient.

The university held a similar drill last year, during which students dealt with the fallout of an imaginary bus crash with many casualties.

“Something terrible like this could always happen, and as nurses we’ll always have the responsibility to lend a hand whenever we can,” Bolduc said.

Follow Nick McCrea on Twitter at @nmccrea213.