Dr. Roy Guerrero, a pediatrician in Uvalde, Texas, described to members of Congress on Wednesday the horrors he saw two weeks ago in the city’s emergency room as he treated wounded and dying students after a gunman massacred an elementary school classroom.

Dr. Guerrero said he had rushed to Uvalde Memorial Hospital on May 24 and found parents already outside the building, yelling their children’s names, sobbing and begging for information.

“Those mothers’ cries, I will never get out of my head,” Dr. Guerrero told the House Committee on Oversight and Reform during a hearing on gun violence. He added: “I know I’ll never forget what I saw that day.”

He said the first wounded student he saw, upon entering the emergency room, was Miah Cerrillo, an 11-year-old student who had smeared blood on herself to hide from the gunman. Miah also testified at the hearing via a video feed on Wednesday.

Dr. Guerrero said Miah had been bleeding from a shrapnel wound to her shoulder, and that her face was in shock.

“Sweet Miah,” Dr. Guerrero said, noting that he had known the girl for her whole life and that she had survived major liver surgeries as a baby. Dr. Guerrero grew up in Uvalde and attended the same school, Robb Elementary, as a child. He said he ran outside to tell her parents that she was alive.

Speaking to the House committee, Dr. Guerrero described returning to the emergency room to horrifying sights: two children who he said had been “pulverized” and “decapitated” by bullets.

“Innocent children all over the country today are dead because laws and policy allows people to buy weapons before they’re legally old enough to even buy a pack of beer,” Dr. Guerrero said. “They’re dead because restrictions have been allowed to lapse.”