On Monday morning, Dr. Joseph Fusco had begun what seemed like a normal workweek at the Monroe Carell Jr. Children's Hospital at Vanderbilt, where he specializes in children's cancer and neonatal surgeries.

Soon after 10 a.m., after his routine morning rounds, the pediatric surgeon was on his way to the operating room when a page alerted him: An ambulance was en route to the Nashville hospital carrying a gravely wounded gunshot victim.

Then came another page, and another, and another, and another. Three of the victims, he soon learned, were only 9 years old.

Four miles from Vanderbilt's campus, a 28-year-old shooter had opened fire at the Covenant School, a private elementary school on the grounds of a church in Nashville's Green Hills neighborhood. Six were killed: head of school Katherine Koonce, custodian Mike Hill, substitute teacher Cynthia Peak and three third-grade students — Evelyn Dieckhaus, William Kinney and Hallie Scruggs.

In total, five of the victims of Monday's school shooting were transported to the Vanderbilt University Medical Center and its affiliated children's hospital, hospital officials say.

"You're in a bit of shock when you get something like that," Fusco said, recalling his reaction to seeing the pages. "This should never happen to children."

In a blink, the machinery of the Level 1 trauma center whirred to action: Operating rooms were readied with surgical instruments and blood for transfusions. Administrators prepared a family area. Hospital security was alerted. Staff of all kinds assembled — nurses, nurse practitioners, physicians, surgeons, spiritual leaders, social workers — all ready to spring to action.

Fusco, on call that day as an emergency pediatric trauma surgeon, was among the doctors who saw the arriving patients for an initial rapid assessment.

But by the time they arrived at the children's hospital, the three young patients had already died.

"The wounds that are present on these children's bodies — I mean, not to be gruesome, but I think suffice to say that injuries from those weapons are essentially unsurvivable for children," he said.

Children's bodies are especially susceptible to damage from high-powered weapons

Police say that the shooter, identified by authorities as Audrey Hale, used three guns in the attack, including an AR-style rifle.

Most firearm deaths and injuries are caused by handguns, whose bullets typically pierce straight through targets. By contrast, military-style rifles fire with such power that their bullets can pulverize bones and vital organs.

"As a trauma surgeon, I can tell right away if somebody has been shot with a handgun versus a high-powered assault rifle," said Dr. Alex Jahangir, who heads the Vanderbilt Center for Trauma, Burn and Emergency Surgery. The rifle "is exponentially worse, obviously," he added.

Children are even more susceptible to severe injuries from military-style rifles, the doctors said. Their bodies are more compact, their vital organs smaller and closer together, making it easier for a single bullet to do catastrophic damage.

Gunshot wounds are a fact of life for trauma surgeons in major U.S. cities, even for pediatric surgeons like Fusco — firearms are the leading cause of death for children in the U.S., killing thousands each year.

Still, despite more than a decade of training and experience as a surgeon, Monday's shooting was the first time he had ever seen a child "assaulted with something like this," Fusco said.

"It goes against all of the training that I've had for so long," he said. "Throughout residency, fellowship, you see thousands and thousands of patients. You're taught to help and do everything you can to help them."

To find that he couldn't left him and his colleagues in despair.

"You're so geared up. We're so well-prepared to help. We've had nurses drive in from home to the emergency department. Everyone is there," he said. Instead, all they were left with was "the feeling of sheer helplessness when you have patients that come in with injuries that are just completely unsurvivable."

Hospital staff were prepared but left emotionally drained

Officials at VUMC overhauled the hospital's mass casualty response plan after a man opened fire on a music festival in Las Vegas in 2017, killing 60 and injuring hundreds.

The hospital is located in central Nashville, a city famous for its own vibrant music culture. "We said, you know, we're not immune to this," said Jahangir, who helped lead the changes to the plan.

Since then, Vanderbilt has put the plan in action a handful of times each year, Jahangir said. Sometimes the mass casualty event is a tornado. Other times it's a bad accident on the interstate. Occasionally, it's a mass shooting — though school shootings are rare.

"It became evident that this was serious and this was maybe a little different from what we've experienced before, in that it's what I think many of us, especially those of us with young children, always dread," he said of the alerts Monday.

On Monday, the alert had ended by the early afternoon, once it was clear that no more victims would be arriving, meaning the staff and facilities on standby — the surgeons, the nurses, the blood bank, the operating rooms — would no longer be needed.

About 20 doctors and nurses gathered in a conference room near the emergency department to process the morning's events. Some sat quietly. Others cried. "Being in that room, with people being exceptionally upset, expressing that emotion, it's difficult," Fusco said. "The silence is deafening."

"I've been a physician for 20 years. You're trained, especially back then, to kind of just be tough, and just deal with it. And I think we've realized that's not the right way to approach it," Jahangir said. "We're not immune to the emotions that happen."

As the city mourns the six victims of the shootings, plans for their funerals have been set. The first, for third-grader Evelyn Dieckhaus, will take place Friday afternoon; she will be laid to rest Saturday in a private family burial. Others will continue over the weekend and into next week.

"Everyone is still shaken up in the hospital just like we are in the community," Jahangir said. "It hits home."