Excerpts from abcnews.go.com:

For students from elementary to high school, the Sept. 11 terrorist attack isn’t a memory. It’s history. A new HBO documentary that debuted on the event’s 18th anniversary treats it that way.

The necessity of her project, “What Happened on September 11,” struck filmmaker Amy Schatz when a third grade girl told her about a playdate where she and a friend Googled “Sept. 11 attacks.”

“When a child does that, what he or she finds are some pretty horrific images that are not necessarily appropriate for kids,” Schatz said on Tuesday. “So I felt a responsibility to try to fill that void and try to give kids something that isn’t horrifying and kind of fills in the gap.”

She worked with the Sept. 11 remembrance museum on the story, filming two men who work there giving presentations to third graders. Stephen Kern, who worked on the 62nd floor of the World Trade Center’s North Tower, talks about being evacuated. Matthew Crawford, whose father was a firefighter who died that day, discusses his experience. 

The film tells of Osama bin Laden and his activism that started with the Soviet Union’s invasion of Afghanistan. But it never truly answers the whys. Maybe no one can.

The film doesn’t avoid some of the terrible images of the day: the second plane striking the World Trade Center and resultant fireball, the collapse of each tower and the giant clouds of debris that billowed through the canyons of city streets. 

As part of her research, she interviewed alumni of Stuyvesant High School near the World Trade Center site. But the memories of what they saw, heard and smelled that day — and the uncertainty of how they would get home from school — proved too raw. That’s why “In the Shadow of the Towers: Stuyvesant High on 9/11” is a separate film that premieres on HBO three hours after the first one.