Miah Cerrillo, a fourth-grade student in Uvalde, Texas, who smeared a dead classmate’s blood on herself to avoid being targeted by the gunman who killed 19 students and two teachers in her classroom, described the nightmarish attack in a video played before members of Congress on Wednesday.

Miah, 11, was among several people who testified at the hearing on gun violence. In the pre-recorded video, she said she had been watching a movie with her classmates when one of her teachers got an email and then moved to lock the door. The teacher had told students, “Go hide,” she said, and they hid behind backpacks and their teacher’s desk.

“He shot my friend that was next to me,” Miah said. “And I thought he would come back to the room.”

She took blood from her friend and rubbed it over herself so that she would appear dead, and she then called 911 from her teacher’s phone, asking for the police.

“I said we needed help,” she said.

In the video, she was asked what she wanted to come from the mass shooting.

“To have security,” she told members of Congress. She shook her head when she was asked if she felt safe at school. “I don’t want it to happen again.”

Her father, Miguel Cerrillo, testified briefly in Washington, saying that Miah had changed since the shooting. He pleaded for some kind of change to protect children in school.

“I came because I could’ve lost my baby girl,” Mr. Cerrillo said through tears and sniffles. “And she’s not the same little girl that I used to play with and run with and do everything, because she was Daddy’s little girl.”

“I wish something would change,” he said. “Not only for our kids, but every single kid in the world, because schools are not safe anymore.”