‘It’s a scene that you never want to see.’ An official recounts a day of bloodshed.

When Eulalio Diaz began hearing the roaring sound of nonstop ambulances Tuesday afternoon, he sensed something had gone terribly awry in Uvalde, a town of about 16,000 where most people know their neighbors by name.

Mr. Diaz is one of the town’s justices of the peace, assuming some of the duties of a coroner, including identifying the dead. He was on duty that day and had never seen so much carnage: The last recorded murder in Uvalde took place at least a year ago, he said.

By the time he arrived at Robb Elementary School, after 2:30 p.m., the authorities had descended on the small-town school, which teaches second, third and fourth graders.

Moments later, he was informed of the harrowing reality: A gunman had stormed into the school and fired several rounds at defenseless children. He requested aid from the medical examiner in Bexar County, which includes San Antonio.

Some time after 5 p.m., he said, Mr. Diaz and two representatives from the big city’s coroner’s office walked into the crime scene. Even though he had been told there were at least 16 or 17 fatalities, he was not prepared for what he witnessed.

“My heart dropped,” he said. “I knew there were going to be children. I know their parents. I know their grandparents.

“It’s a scene that you never want to see, that you never imagined. It stays in your mind. My heart drops for them and for their families immediately.”

He and his colleagues tried to remain calm and proceeded with the painful task of identifying the small victims. Mr. Diaz, a father of two children in eighth and twelfth grades, said he worked hard to release the victims as soon as possible to area funeral homes so that their loved ones could see them again: nine on Wednesday afternoon and the remaining on Thursday or in the next few days, he said.

“It’s a very tough job,” he said. “It’s a small community. We all know each other. It’s heart-wrenching.”

Mr. Diaz, a lifelong Uvalde resident, said he later learned he had known some of the victims, including one of the town’s beloved teachers, Irma Garcia, who he said was a high school classmate.

“I don’t want to ever see it happening again anywhere else right now,” he said. “I know everyone, their parents, their grandparents. I’ve been trying to hold it together.”