It’s an overtime shift, and I’m working with Garrett, a 22-year-old who just started working as an EMT a month ago. He tells me he’s hoping to gain some experience in dealing with patients in anticipation of starting medical school next year.

It turns out to be a busy morning and Garrett handles himself pretty well on a couple of easy jobs — a teenage female with abdominal pain, and an elderly male with a broken arm. “If your medical skills end up being as good as your bedside manner,” I tell him, “you’ll make an excellent doctor.”

He blushes and tells me he’s anxious because he hasn’t seen a dead person yet, or performed CPR. I say that when I started I was scared to death about doing CPR — a brutal intervention — on an elderly patient’s chest. The intimacy of it, the ugliness: Your face is 12 inches away from the patient’s. “The first dead face you see will stay with you for the rest of your life. Especially if it’s someone you do CPR on,” I say.

I recount my first DOA, a woman we found on the sidewalk around Halloween. Her battered, swollen face was like a mask.

After lunch, our unit and a paramedic unit get a call for a Priority 1 job, a 50-year-old male in full cardiac arrest in an apartment building in Gravesend. I tell Garrett we’ll probably beat the medics there, and remind him to bring the defibrillator, the device that delivers shocks to jumpstart the heart.

We arrive and see a fire truck. The firefighters tell us it’s an “83,” a DOA, and introduce us to the patient’s mother, an elderly woman who appears to be mentally impaired. She tells us she couldn’t wake her son for dinner last night or this morning for breakfast.

“He’s always been a deep sleeper, that boy,” she says, shaking her head.

We enter the apartment and see the male lying face up on the couch. Telltale signs of death are everywhere: rigor mortis, dependent lividity, the smell of decaying flesh. He has to have been dead for a couple of days. “No wonder she couldn’t wake him,” I quip to Garrett, and then radio the dispatcher to “87” (cancel) the medics and have NYPD respond. I start to explain to Garrett that the police have to respond to every DOA, but when I look over my shoulder I see he is still in the hallway. I go back and ask him if he’s waiting for me to roll out the red carpet. He’s pale.

“The firefighters say he’s dead,” he says.

I cough politely in front of the firemen and tell Garrett to go inside and see the body — he needs to be able to recognize the signs that confirm death. He hesitates. I smile and say, through gritted teeth, “Get your butt in there and look at that body.” This is a necessary part of the job, especially for a future doctor. I point to the bedroom. “Now.”

He walks like a man heading to the gallows. PD arrives, and I sit on the hall stairs to write up the call. When Garrett comes back out, he looks older. “Well?” I say. He says nothing. I finish the paperwork and head outside.

Before I can say anything, we get another cardiac arrest, this time in a nearby nursing home. We respond and find an apathetic staff performing CPR on a 95-year-old woman. We continue their efforts: Garrett delivers oxygen through a mask, and I can feel the patient’s fragile ribs crack under the necessary pressure of my chest compressions.

Medics arrive, and after 30 minutes of working the patient, the FDNY telemetry doctor tells them to call the code. Bloody medical waste lies scattered around the patient, who looks mangled. We clean her up as best we can and leave with the medics — the nursing home will arrange removal of the body. The medics are affable, and I converse freely with them, but Garrett is silent. He opens the side door of the ambulance and throws the equipment bag in. “What’s wrong?” I ask, and he starts to cry: about his parents getting older, about the uncaring staff, about how sad it all is.

The reality of old age and death can be traumatic for the young and uninitiated, who often feel invincible. His loss of innocence is palpable. I put my arm around him and try to find the words, but of course there are none, and I realize that this heavy silence is exactly what I experienced with my first partner, and my first DOA, several years ago.

Ms. Klopsis is an emergency medical technician on an ambulance in Brooklyn. This column details her observations and experiences. Some names and identifying details have been changed to protect the privacy of patients.