"We did what we're trained to do,'' Schumacher explained. "When you see a patient in need, you go about seeing the problem is fixed. You go into auto pilot.''
As Schumacher and his colleagues soon discovered, the patient was not an isolated victim. Within minutes, a series of ambulances unloaded bloodied patients, many with severely damaged extremities that required tourniquet splints and emergency surgery.
"It wasn't until the fourth or fifth victim went through that I even had a chance to ask, 'What happened here?''' Schumacher said. Thirty-nine of those injured in the bombings were transported to the trauma center where Schumacher was working.
Schumacher had planned to watch the marathon from the finish line that day with friends visiting from his native Louisiana, but he was called into work at the last minute. He expected a busy afternoon, but nothing -- not even extensive emergency trauma training -- could prepare him for what he witnessed that day.
While amputations are not uncommon in hospitals, they are often limited to diabetic or elderly patients.
"This," said Schumacher, "was a totally different patient population. We were treating teenagers, people in their 20s, athletes, newly married couples, an athletic trainer.
"No matter how bad it was, our immediate goal was to save their extremities.''
The single-mindedness required to manage the sheer numbers of the patients, along with the severity of their injuries, prevented Schumacher from reading news reports or viewing television footage of the tragedy. He was simply too busy.
"Almost everyone around the country knew more than I knew,'' Schumacher said. "It was really was about two weeks before I was able to fully take in what happened.''
Once he had a chance to reflect on what occurred, as well as meet with his patients and their families during their ongoing recovery process, Schumacher, who has never run a long distance race, made the decision to run Boston in 2014.
"I felt a calling to do this,'' he said. "I wanted to represent those patients who are still working towards getting back on their feet. I want to honor them, out of respect for them.''
Schumacher was a former high school football and basketball player but only a recreational runner. His busy work schedule has made training arduous, often requiring late-night runs after completing 14-hour shifts at the hospital.
When he's sapped of energy, or lacking motivation to train, he focuses on Gillian Reny, a high school senior and avid dancer who was at the finish line with her mother, Audrey, and father, Steven, waiting for her sister Danielle to cross.
Reny was critically injured in the blast and suffered significant damage to both legs, but after many months and multiple surgeries at the Brigham, she is walking again and enjoying her freshman year at the University of Pennsylvania.
Her grateful family started the Gillian Reny Stepping Strong Fund to help generate research dollars for saving limbs and bone and skin regeneration.
Thanks to the BAA, which chose his essay as worthy of earning an official race entry, Dr. Chase Schumacher will run the Boston Marathon to support both Gillian and the Stepping Strong Fund.
This year, Schumacher will not be on call at the Brigham. He vows to make it to the finish line -- as a runner, a medical advocate and a symbol of hope and healing.