PHILADELPHIA — I remember the first time I saw a teenager die. He came to Temple University Hospital in the back of a police cruiser with three bullet holes in his chest. He was wearing bluejeans that had turned red.

The nurses cut them off and threw them at the end of the bed. The bluejeans that were no longer blue dangled for a while, eventually falling into the puddle of blood collecting underneath them. After nothing more could be done to save him, the bed that held his thin body was rolled away, leaving streaks of blood across the floor.

As a first-year medical student, this image haunted me. I think it always will.

Over and over, young Americans from Parkland, Fla., to North Philadelphia are carried into ambulances and the back seats of police cars and rushed to a hospital. The emergency room nurses and doctors lift them onto stretchers. If they are awake, they may ask if they’re going to die. The doctor tells them no.

Once inside, the trauma team yells out locations of holes in their body. The medical student tapes paper clips to each bullet wound so that they’re visible on X-ray. If the heart stops, doctors break through the sternum with a mallet and a chisel.