(somber music) - [Narrator] The Cook County Coroner's Office led an official investigation into the cause of the fire nine days later.

- What could I say?

I mean, it happened, but- - You have the right to say anything you want to.

- I don't want it to happen again.

If we have other children, you're going to send other children to school, you don't wanna be afraid again.

Everybody has their empty feeling within themselves, and we just don't want it to happen again- - Well, maybe- - In the future.

- Maybe out of this, may come a lotta good.

- That's the one thing- - We hope.

- That I hope that my son didn't lose his life for nothing.

- [Narrator] Speculation arose that students had been smoking in a stairwell.

- They brought the police in, and we were questioned by the police.

"Do you know who smoked?

Did you smoke?

Did you see anybody loitering around?"

- We took police crime lab photographs of the scene.

We obtained physical evidence, such as the stair, a step from the stairwell that led down on into the area where the fire appeared to have started.

- [Narrator] The investigation concluded without providing any real answers.

But the National Fire Protection Association issued a scathing report one year later, accusing authorities of housing children in fire traps.

- There was no fire alarm that was connected to anything.

It was just a bell that rang in the building.

No sprinklers.

The fire extinguishers were seven feet where no one could get to 'em.

- [Narrator] A private inspector made a startling conclusion about the cause of the fire.

He called it arson, but the public never learned about his findings.

- Mom was angry at the church for not giving us more information and not, you know, it just seemed like they wanted to wash their hands with it, you know?

- [Narrator] The trail went cold for years until law enforcement questioned a 13-year-old boy about setting fires in Cicero, a Chicago suburb.

The boy took a polygraph test and confessed to starting another fire when he was a fifth grader at his previous school, Our Lady of the Angels.

- He said, "I'd asked the teacher for permission to go to the bathroom.

Instead of going to the bathroom, I went to the school basement.

I found a 55-gallon cardboard drum."

He said, "I threw four or five matches, wait til really started going and then I went back to my classroom."

(fire crackling) - [Narrator] Judge Alfred Cilella dismissed the boy's confession in family court, ruling it had been improperly obtained.

- I want to be very sure in this case.

I took the entire matter under advice.

- In my opinion, from everything I've read, I feel he was the one.

I think the criminal justice system has an obligation to protect innocent people from people like this.

The criminal justice system failed.

- [Narrator] Cilella exonerated the boy of starting the school blaze but found him guilty of setting four other fires in Cicero.

The judge ordered the youth sent to a juvenile detention facility.

He denied setting the school fire before passing away in 2004.

- If this person did it, he should've somehow paid for it, But maybe he did.

He probably had his own torment.

- [Narrator] The official cause of the fire remains undetermined.

The archdiocese paid $3 million in wrongful death and personal injury lawsuits.

Mayor Daley set up a fund with contributions from all over the world to cover victims' medical costs.

- I remember my father saying, you know, "This doesn't bring my kids back."

- [Narrator] The sad truth is that many other schools, parochial and public, lacked adequate safety devices.

The fire might have happened at any one of them, but it was Our Lady of the Angels that suffered.

(somber music) The tragedy led to a nationwide overhaul of fire safety laws at schools.

- I don't think that's quite redemption, but it is grace, a grace that came out of a tragedy.

- [Narrator] Not a single child has died in a Chicago school fire since.