Warning: Details of this testimony may be distressing to some readers.

The parents of 10-year-old Alexandria Aniyah "Lexi" Rubio, who was killed in the Uvalde mass shooting in Texas, delivered tearful testimony at a U.S. House committee on gun violence Wednesday.

Felix and Kimberly Rubio say the Grade 4 student had won the Good Citizen award on the morning of her death at Robb Elementary School, and also made honour roll.

Kimberly Rubio said the decision to leave Lexi at school after the ceremony is a decision that will haunt her for the rest of her life.

She described her ordeal of learning about the shooting, and trying to find out whether her children were safe. She recalled running barefoot towards the school due to heavy traffic in the area, before learning that her daughter was among the 19 children killed.