Miah Cerrillo, a pupil at Robb Elementary School in Uvalde, told lawmakers in a pre-recorded video that she watched a teacher get shot in the head before looking for a place to hide.
“He told my teacher goodnight, and shot her in the head.
“When I went to the backpacks, he shot my friend… and I thought he was going to come back to the room, so I grabbed blood and put it all over me.”
“I thought he would come back so I covered myself with blood,” Miah told the House panel. “I put it all over me and I just stayed quiet.” She called 911 using the deceased teacher’s phone and pleaded for help.
She added: “"I don't want it to happen again”
Miah's father, Miguel Cerrillo, said his daughter is suffering from lingering trauma from the event.
"She's not the same little girl I used to play with," he said tearfully. "Schools are not safe anymore. Something really needs to change."
Nineteen children and two teachers died when an 18-year-old gunman opened fire with an AR-15-style rifle inside the school on May 24.
Her mother, Kimberly Mata-Rubio added: "Somewhere out there, a mom is hearing our testimony and thinking to herself, 'I can't imagine the pain'," "Our reality will one day be hers, unless we act now."
Uvalde paediatrician Dr Roy Guerrero also spoke to the committee to describe the fatal injuries he witnessed.
"Two children, whose bodies had been pulverised by bullets fired at them, decapitated, whose flesh had been ripped apart. That the only clue as to their identities were the blood-spattered cartoon clothes still clinging to them.”
It is the second day lawmakers have heard testimony on the nation’s epidemic of gun violence.
On Tuesday, a Senate panel heard from the son of an 86-year-old woman killed when a gunman opened fire in a racist attack on black shoppers in Buffalo, New York, on May 14. Ten people died.
The testimony at the House Oversight Committee comes as lawmakers are working to strike a bipartisan agreement on gun safety measures in the aftermath of back-to-back mass shootings.
Carolyn Maloney, the panel’s chairwoman, called the hearing to focus on the human impact of gun violence and the urgency for lawmakers to enact gun control legislation.
“I am asking every member of this committee to listen with an open heart to the brave witnesses who have come forward to tell their stories about how gun violence has impacted their lives,” Ms Maloney said in opening remarks.
“Our witnesses today have endured pain and loss. Yet they are displaying incredible courage by coming here to ask us to do our jobs.”
The panel also included testimony from Zeneta Everhart, whose 20-year-old son Zaire was wounded in the Buffalo mass shooting.
Ms Everhart told lawmakers it was their duty to draft legislation that protected Zaire and other Americans. She said that if they did not find the testimony moving enough to act on gun laws, they had an invitation to go to her home to help her clean her son’s wounds.
“My son Zaire has a hole in the right side of his neck, two on his back, and another on his left leg,” she said, then paused to compose herself.
“As I clean his wounds, I can feel pieces of that bullet in his back. Shrapnel will be left inside of his body for the rest of his life. Now I want you to picture that exact scenario for one of your children.”
President Joe Biden discussed the recent incidents of gun violence in the US as he appeared on Jimmy Kimmel Live! during his first in-person appearance on a late night talk show since taking office.
Asked by Kimmel why he had not issued an executive order to help stop such tragedies occurring, Biden said he did not want to “emulate (Donald) Trump’s abuse of the Constitution”.
“I have issued executive orders, within the power of the presidency, to be able to deal with these, everything having to do with guns, gun ownership, all the things within my power,” he said.
“But what I don’t want to do, and I’m not being facetious, is emulate Trump’s abuse of the constitution and constitutional authority.”
He continued: “I often get asked, ‘look, the Republicans don’t play it square, why do you play it square?’
“Well, guess what? If we do the same thing they do, our democracy would literally be in jeopardy.
“It’s not a joke.”
It comes after Matthew McConaughey made emotional opening remarks at the top of a White House press briefing.
The actor called on Congress to “reach a higher ground” and pass gun control legislation in honour of those killed during the incident in Uvalde, his home town.
During his speech he related personal stories of a number of the victims, displaying the artwork of one girl and the trademark green Converse trainers worn by another.
McConaughey acknowledged that gun legislation would not end mass shootings but suggested that steps can be taken to lessen the chances of such tragedies happening so frequently.
The United States House of Representatives has voted to set a minimum age of 21 for buying semi-automatic weapons in response to recent mass shootings, including in New York and Texas.
The vote was part of a wide-ranging gun control bill passed on Wednesday that would raise the age limit for purchasing a semi-automatic rifle and prohibit the sale of ammunition magazines with a capacity of more than 15 rounds.