The girl spotted an unfamiliar box containing Hanlon's dusty, banged up old firefighter's helmet.
"Dada, what's that?" she asked.
Hanlon's mind raced back 15 years when he and hundreds of other first responders rushed inside the World Trade Center after terrorists flew hijacked airliners into the North and South Towers.
"Oh, that's what Daddy used to do for a living," he explained.
She tried to ask a few questions, Hanlon recalled during a recent interview for the documentary, "9/11: Fifteen Years Later."
Someday he'll tell her about that day, he said. "I don't know when that conversation will be, she's so young."
Hanlon -- a member of Ladder Company 1, Engine 7 -- was working with fellow filmmakers and friends Gedeon and Jules Naudet on a documentary about the New York City Fire Department. From the moment the planes hit and in the aftermath, they became witnesses to history, creating a rare visual record of the horrific and heroic events.
Of the 2,977 victims who died on 9/11
in New York City, at the Pentagon and near Shanksville, Pennsylvania, 343 were New York City firefighters.
Now, as another milestone year passes, the men featured in the documentary reflected on what has changed since that day, the lessons they've learned and how future generations should respond to terrorism.
The battalion chief featured in the film is now traveling the globe, sharing new ideas on how to combat shifting terrorist tactics. He's worried about evolving attack methods and how to prepare. The film's rookie firefighter is now a lieutenant and father who has maintained his idealism in what he said is a more fear-mongering and divisive world.
And Hanlon, who helped create the documentary, is now an episodic TV director
, based in Southern California. Nonetheless he'll always be proudest of his firefighting days, saying, "Until the day I die, I'll be a New York City firefighter."
Hanlon thinks of 9/11 as a day of heroism and love. "It was a day where evil tried to overtake good, and you know, I think good won out."
For those who suffered from survivor's guilt, he said it was a day of loss.
The pain "has eaten some guys up," Hanlon said. Children of victims have been forced to grow up without grandparents, parents, brothers and sisters. The loss surrounds the feeling that "you're here — and so many people are not," he said.
Losing friends and colleagues has made Hanlon feel a "responsibility to live my life the best as I can for those who are not here."
"I'm married. I have a child. I have another career that is successful," he said. "And I use all that to help myself move forward."
Hanlon first met Tony Benetatos in 2001, when he was a rookie firefighter — what firefighters call a "probie."
"You're not a fireman in the first 9 months," Hanlon explained. "You're really a probationary firefighter. Tony was my probie."
Back then, Benetatos was a bright, 22 year old who was so new and untested on 9/11 that "everybody was worried about him," Hanlon recalled.
Now 37, Benetatos has risen through the ranks of the New York Fire Department to become a lieutenant.
A firefighter is responsible for their task, said Benetatos, while a lieutenant has to make sure the firefighters are safe, so no one gets hurt.
"It's a terrifying responsibility," he said. "The last thing I want to be responsible for ... is the loss of the life of somebody under my command."
He's noticed some big changes in America since 9/11.
The nation, he said, has shifted negative. "All our foreign policy discussion is terrorism. All of our politics is divisive," said Benetatos. "Everything is about fear and who to be afraid of and who the bad guys are and who the good guys are. Maybe I'm an idealist, but that is not how I remember the world prior to the 11th."
For the past 15 years the nation has been at war, Benetatos pointed out. The attack on the World Trade Center "was used as a pretext for foreign interventions, for conflict. ... And there are people, there are children who don't know our country not at war."
Hanlon notes that many fire department probies these days are veterans of those wars in Iraq and Afghanistan. "I've met a couple of them and they're squared away," he said. "It makes you feel good."
Benetatos joined years ago because he wanted to contribute to society and his community. Now, being able to do something that has a positive effect on the world around him is one of the main reasons why he's still a firefighter.
He's a married father to two daughters — and a third child is on the way.
The former probie is also entering neighborhood politics — running for a seat on a local county committee.
He admits he was "more naive" when he became a firefighter back in 2001, but, Benetatos said "I'd like to think that I have retained my idealism."
Until the planes hit, the documentary was supposed to focus on Benetatos as he learned the ropes of firefighting. The filmmakers were two brothers: Gedeon and Jules Naudet.
On the morning of the attacks, Jules Naudet was shooting video with fire department Battalion Chief Joe Pfeifer when he heard American Airlines Flight 11's engines overhead. He pointed the camera skyward and captured one of the only videos showing the jet crashing into the North Tower.
At that moment the mission of the documentary changed.
"I didn't help anyone. I didn't save anyone. But I could film," Jules Naudet said. "I could witness. I could show people what had happened and how these amazing everyday people — these first responders, firefighters, people in the building — the good they did."
After the first plane crashed, he and Pfeifer headed for the North Tower, where Jules shot more video and Pfeifer directed firefighters who were helping thousands of people escape.
When the North Tower collapsed, Jules jumped between two cars to avoid the giant cloud of debris coming toward him. Pfeifer jumped on top of Jules, "protecting me as he did that day."
Meanwhile, Gedeon Naudet filmed the wait and worry at the firehouse before making his way toward the towers to document scenes of Lower Manhattan.
By the end of the day, Jules was convinced he'd lost his brother, until he saw Gedeon walking into the firehouse with a big smile. "He's my big brother — I felt like a kid again," Jules recalled.
A year later, the firehouse hosted Jules' wedding, which "celebrated a new beginning that they gave us, because they saved me that day."
Now, Jules has two children and Gedeon — a newlywed — is expecting his first. "My baby is due around September 11, which is a bit weird," Gedeon said. "So I'm freaking out."
A lot has changed in 15 years for the 9/11 survivors in that firehouse. "Most of the guys who were married are divorced," Gedeon said. "Most of the guys were were single at that time are now married."
Those who got hit hardest by survivor's guilt "are now doing better," Gedeon said. "The ones who are doing miserably are the ones who are not with their families anymore."
"The truly horrible thing," Jules said, is that "September 11 is still killing."
About 127 names of firefighters whose illnesses were linked to 9/11 — including working at Ground Zero — are on a wall at New York Fire Department headquarters in Brooklyn.
Hundreds of chemical compounds — including known carcinogens — were present in the dust surrounding Ground Zero
Potential cancer-causing agents such as asbestos that coated the World Trade Center buildings' lower columns, and benzene, a component of jet fuel that stoked uncontrollable fires, have long been a cancer concern for researchers
Scientists have expressed concern about the high volume of particulates and gases inhaled by responders, survivors and neighborhood residents.
The battalion chief
Like Gedeon Naudet and Benetatos, children have entered the life of former chief Pfeifer in the years since the attacks.
In Pfeifer's case, he's become a grandfather. Now he thinks about how his young granddaughter will view 9/11, when she's old enough to hear about it for the first time.
"With my granddaughter," he said, "I see things the way they should be seen really — through her eyes — the eyes of innocence."
The former battalion chief now performs a larger role as the department's chief of counterterrorism and emergency preparedness.
He lost his brother Kevin who died helping people escape the North Tower.
"9/11 changed everyone," Pfeifer said. "It's changed the way we think. It's changed the way we do things and it's dramatically changed the fire department."
As counterterrorism chief, Pfeifer now thinks globally about new ways to combat terrorism. He collaborates with others to improve tactics with first responders worldwide — including Paris — where last November's attack by ISIS killed more than 120 people.
Pfeifer is proposing new terrorism response strategies. He wants new tools to manage complex responses to big crisis situations. He envisions an electronic command board that integrates live video and digital blueprints from the scene that show where units are operating on a floor plan in real time.
He also says "the Vertical Threat" -- attacks on high-rise buildings using methods different from 9/11 -- keeps him up at night. "We've gotten better protecting our planes," Pfeifer said, making it harder for bad guys to launch another 9/11. "But what we're also seeing is that it takes less skills to have an attack."
Benetatos said we can all take a lesson from firefighters — who in some ways are trained to run toward danger, instead of away from it.
"If you see a problem, if you see something that needs to be dealt with, take personal responsibility and fight," Benetatos said. "Fight for what you believe in. Try to make a difference. And even if it looks like nothing's happening ... continue fighting, because that's the only way we accomplish anything."
Hanlon, the retired firefighter, doesn't know when he'll tell his daughter about the events of 9/11.
"Hopefully I'll be a little bit wiser by that age," he said. "And if she wants to hear about it, I'll tell her about it."