WARNING: Some of the following images are graphic and are NSFW.

On this day sixteen years ago, two planes collided with the World Trade Center buildings in New York City. The date is now remembered as a tragedy in which nearly 3,000 American citizens were killed. Once believed to have been a terrorist attack by al-Qaeda, new evidence suggests that the towers instead crumbled as a result of a controlled demolition. In a paper published by Europhysics News, scientists concluded exactly this.

The paper noted,

“It bears repeating that fires have never caused the total collapse of a steel-framed high-rise before or since 9/11. Did we witness an unprecedented event three separate times on September 11, 2001? The NIST [U.S. National Institute of Standards and Technology] reports, which attempted to support that unlikely conclusion, fail to persuade a growing number of architects, engineers, and scientists. Instead, the evidence points overwhelmingly to the conclusion that all three buildings were destroyed by controlled demolition. Given the far-reaching implications, it is morally imperative that this hypothesis be the subject of a truly scientific and impartial investigation by responsible authorities.”

The investigation was carried out by a number of reputable scientists, including Anthony Szamboti, a mechanical design engineer; Steven Jones, a former professor of physics at Brigham Young University; Robert Korol, a professor emeritus of civil engineering at McMaster University in Ontario, Canada and a fellow of the Canadian Society for Civil Engineering and the Engineering Institute of Canada; and Ted Walter, author of Architects & Engineers for 9/11 Truth’s Beyond Misinformation: “What Science Says About the Destruction of World Trade Center Buildings 1, 2 and 7.” Read the paper, entitled “15 Years Later: On the Physics of High-Rise Building Collapses,” to learn more.

Though the reason(s) the towers collapsed remains a topic of controversial discussion, the fact remains that many individuals and families continue to suffer emotionally as a result of losing loved ones. Hopefully, the following images (compiled by Bored Panda) which have been rarely seen provide clarity on what happened that tragic day and, as a result, help many find peace.

Following are 15+ rare images that were taken in New York City on September 11th. The images were obtained from professional and amateur photographers, yet they all have one thing in common: they document a happening which is shrouded in mystery and will continue to affect the world’s population for years.

#1 A Knot Of Bystanders At Park Row And Beekman Street Look Up As The South Tower Begins To Collapse

Credit: Patrick Witty

#2 At Rector Street And Broadway, A Photographer Leaned Out His Window With A Medium-format Camera And Caught The Moment Before The Second Plane’s Impact

Credit: Rob Howard

#3 People Falling From The Towers

Credit: David Surowiecki

#4 A Man Has A Job To Do

Credit: Melanie Einzig

#5 As Seen Through A Fish-Eye Lens From An Apartment Four Blocks Away, Smoke Streams From The North Tower Within Minutes Of The First Plane’s Attack

Credit: Patricia McDonough

#6 People Run Down Broadway As A Smoke And Dust Cloud Comes Up The Street From The Collapsing World Trade Center Buildings In New York

Credit: Kelly Price

#7 American Airlines Flight 11 (Visible In The Upper Right-Hand Corner Of The Photo) Approaches The North Tower Of The World Trade Center On September 11, 2001

Credit: Wolfgang Staehle

#8 The South Tower Disintegrates, Raining Debris Behind A Cross Atop Trinity Church

Credit: James Nachtwey / VII for Time

#9 South Tower Of The World Trade Center Collapsing

Credit: Bolivar Arellano

#10 Not Yet Realizing A Terrorist Attack Was In Progress, Architect And Amateur Pilot Isabel Daser, Eight Months Pregnant, Asked A Co-Worker To Take Her Portrait As A Record Of The Day

Credit: Daser Bessler

#11 The Second Plane Flew Directly Over My Head And Slammed Into The South Tower. It Took Me A Few Seconds To Get My Head Together, And This Was The Shot I Took

Credit: Marc A. Garrett

#12 I Was 4 Years Old And The Picture Was Taken Along The Westside Highway That Morning On 9/11

Credit: AustinSansone

#13 A Lone Man Runs Down Broadway As A Smoke And Dust Cloud Comes Up The Street From The Collapsing World Trade Center Buildings In New York September 11, 2001

Credit: Kelly Price

#14 On A Brooklyn Rooftop Shortly After The Collapse Of The Twin Towers

On a Brooklyn rooftop shortly after the collapse of the Twin Towers, Jenna Piccirillo and three-month-old Vaughan embody innocence and resilience, according to the photographer: “Life continues in the face of disaster . . . despite the horrors we inflict on one another.” Credit: Alex Webb/Magnum Photos

#15 The sight was impossible to look away from

Credit: luke kurtis

#16 Penman Got As Close To The Buildings As He Could, Before Police Put Up A Cordon. But That Meant He Was Right Next To The Buildings When The First Tower Collapsed

Credit: Phil Penman

#17 Smoke Plumes Are Clearly Visible In This Landsat 7 Satellite Image Of New York City Made Early On September 12

Credit: NASA

#18 A Plane Explodes After Hitting The Second Tower Of The World Trade Center As The Other Tower Burns

Credit: Sara K. Schwittek

#19 The Photographer Considered This 9/11 Brooklyn Scene Too Tranquil At The Time. He Decided Not To Publish The Image Widely Until Four Years After The Attacks

Credit: Thomas Hoepker/Magnum Photos

#20 Twin Towers Of The World Trade Center Burn Behind The Empire State Building

Credit: Marty Lederhandler

#21 Several Buildings In The Trade Center Complex Collapsed Following A Terrorist Attack

Credit: Petra Beter

h/t Bored Panda