At a vigil for the victims Sunday night, several blocks from the site of the attack, parent Jim Toole said he didn't volunteer graphic details about the incident to his 9-year-old son, Conor, but is encouraging curiosity. "It's healthy for them to ask lots of questions," he said.
Christina-Taylor died on the scene from a single bullet wound to her chest, when alleged gunman Jared Loughner opened fire, shooting a total of 20 people.
Christina-Taylor was born on 9/11 and had used her birthdate as a source of inspiration during her short life. She was featured in a book about babies born on 9/11 called "Faces of Hope."
"She came into the world on 9/11 and then at 9 years old she leaves it all on this terrible day," father John Green said. "But we wouldn't take it back, any of the nine years we had with her."
"It was all worth it," he said. "But we still believe in this country."
ABC News' Eric Noll contributed to this report.