In the morning of April 19, 1995, Charles (Chuck) Porter IV, banker and keen amateur photographer, left his desk on the 13th floor of the Liberty Bank building in Oklahoma City to go process a loan. No sooner had he arrived four floors below than he heard a tremendous boom and felt the building shaking. His first thought was of a controlled demolition but, looking out the window, he saw debris floating past. His curiosity was piqued.

Porter had never forgotten advice given to him by John White, the Chicago photojournalist and Pulitzer Prize winner, to keep a loaded camera with him at all times. He could not have known that listening to White would take him on a rarefied journey, one in which he would be widely feted, but vilified too. With camera in hand, he went in search of the source of the debris. Rounding the corner a couple of blocks away from the Liberty Bank, he came upon a stupefying site. To Porter, it looked as though someone had taken a giant ice-cream scoop to the Alfred P. Murrah Federal building. The front of the edifice was gone and a large section off-centre had been gouged out from top to bottom. Such was the force of the blast that 324 buildings within a 16-block radius had also been damaged or destroyed. Porter had come upon no controlled demolition, but rather the most devastating act of homegrown terrorism in the history of the United States. He was on the scene before the first responders. There wasn’t a journalist in sight. He immediately began taking photographs.

When I asked Porter to reflect on his emotions at the time, he recalled feeling shocked. But he also believes his camera became his buffer, separating him from the mayhem unfolding before his eyes. He spent around 45 minutes at the scene and shot two rolls of film. He did not know that a bomb planted by Timothy McVeigh had caused the damage and killed 168 people.

By mid-morning, downtown Oklahoma City had been evacuated. With work over for the day, Porter hurried along to his local Walmart, eager to have his film developed. (A footnote to this story contains a coincidental twist that links victims and perpetrator. Porter’s film was processed by the daughter of Officer Charlie Hanger. Earlier that morning on Interstate 35, Officer Hanger had pulled over a vehicle without license plates driven by McVeigh and arrested him for carrying a concealed weapon. McVeigh would languish for two days in the county jail before being linked to the bombing.)

Porter’s first emotion on seeing his developed prints was relief that the images were in focus. It was only when he noticed the effects his photographs had on others that he looked again at them. Unsure of what to do next, he dropped by the local Associated Press office on his way home and was stunned when they asked him how much he wanted for some of the prints. “I had never been paid for a photo in my life,” he told me.

Things moved quickly after that. No sooner was he home than The Times of London called, followed by Time, Newsweek and Life magazines. A FedEx van pulled up to his front door to transport his negatives to New York City. All the major news affiliates, ABC, NBC, CBS, CNN, began calling. By evening, Charles Porter IV was being represented by Sygma, one of the world’s premier photo agencies. The media frenzy would go on for weeks.

The photograph that captured the attention of the world was of a bloodied baby, Baylee Almon, being carried in the hands of firefighter Chris Fields. A second photograph, taken a few seconds earlier, shows police officer John Avery handing over the dead child to Fields, who has touchingly removed his rough firefighters gloves before receiving the grievously wounded infant. Porter’s memory of how he came to take the photographs speaks to pure chance and instinct. “I see something run toward the left corner of my eye,” he recalled. “I turn with my camera; it’s a policeman carrying something. I snap the frame just as the policeman hands it to a fireman. The fireman turns, and he’s holding this infant. He just holds it there for a couple of seconds. I take one shot.”

That one shot would win Porter a Pulitzer prize. It also lends credence to Susan Sontag’s observation that “photography is the only major art in which professional training and years of experience do not confer insuperable advantage over the untrained and inexperienced – this for many reasons, among them the large role that chance (or luck) plays in the taking of pictures, and the bias towards the spontaneous, the rough, the imperfect. There is no comparable level playing field in literature… or in the performing arts… or in film-making…”

Porter would receive other accolades, most notably a British Picture Editor’s Award. But his image also became contentious, albeit inadvertently. A few days after the bombing, with the city reeling, the AP brought together Aren Almon – the mother of Baylee – with Chris Fields, John Avery and Porter. He recalls it was a hard meeting. He felt out of place, “the fifth wheel.” Almon was distraught. Porter remembers saying that he hoped the photograph had not caused her further grief, for that had not been his intent, and being reassured by her that it had not.

Over the years, however, stories emerged to the contrary. Twenty years on from the blast, Aren Almon-Kok, now married and with two children, recalls how awful it had been to see her dead child on the front page of the Daily Oklahoman. Porter’s iconic photograph had enshrined Baylee as the “face” of the tragedy. Some of the bereaved families objected to this. They felt neglected by comparison and resented what they saw as the limelight falling on one family to the exclusion of others. They turned their anger on her. To Almon-Kok, the ubiquitous photograph was a constant reminder of her loss. “I didn’t want to see Baylee dead everywhere every day,” she told one interviewer. When Porter recently sent a Facebook message to Almon-Kok for what would have been Baylee’s 21st birthday, he received a bitter response. She had always hated the photograph, she informed him, and wished it had never been taken.

As Oklahomans affected by the bombing reeled from the magnitude of their trauma, mindful of President Clinton’s plea that “the loss you feel must not paralyze your own lives,” darker forces emerged looking to profit from tragedy. Porter was inundated with offers to use his photograph for merchandise, coffee mugs, T-shirts, gold coins. He turned them all down, except one. He divulged that an agreement was reached with Aren Almon-Kok and Chris Fields for a Sam Butcher’s Precious Moments figurine, but the deal subsequently fell through when the lawyer representing Almon-Kok tried to cut a more lucrative deal on the quiet.

Meanwhile, financial shenanigans were going on elsewhere too. Lester LaRue, an employee at Oklahoma Natural Gas dispatched to the scene by his company, had taken a photograph almost identical to Porter’s. (Porter claims he can immediately tell the difference between the two because his photograph has a sharper focus). LaRue subsequently sold the image to Newsweek, but the gas company claimed ownership of it. The courts ruled in the company’s favour. LaRue lost his job.

Away from the glare of publicity and the hovering entrepreneurs, the victims of the tragedy and the first responders were coming to terms with what they had experienced and witnessed. For Baylee’s mother, the pain endured. Chris Fields developed post-traumatic stress disorder and required counseling. John Avery, according to Porter, received therapy too. And Porter? How did the photographer fare?

Chuck Porter is an uncomplicated man. He left banking a couple of years after the bombing, retrained as a physical therapist and relocated to Texas, where there were better job opportunities. He leads a comfortable suburban life with his wife and two young children. He is not troubled by the accolades he has received in the context of a tragic event, although he is quick to state that he wished the bombing had never taken place. He is proud of his prize-winning photograph. He sleeps well at night. His dreams are not troubled. He harbors no regrets, no guilt. His brow is unforrowed. He has never needed therapy. Having spent some time with him amidst his toy-strewn living room, I have no reason to doubt any of this.

But trauma can be a tenacious beast. PTSD and depression are extreme manifestations of a traumatic response. Far more frequent are subtler tell-tale signs. They should not be regarded as pathological, for their effects are more bemusing than distressing. They can take varied forms, as Porter’s history revealed. In the months after the bombing, he was in demand as a television and radio guest. Tom Brokaw interviewed him. He appeared on the Oprah Winfrey Show. He enjoyed the attention and yet he noticed that whenever he began talking about what he had witnessed, he would break out into a profuse, cold sweat, develop palpitations, experience difficulty breathing and feel his anxiety surge. It wasn’t stage fright. There was no fear. Rather, his body, his physiology had retained an imprint of that traumatic day. At an unconscious level he had been conditioned by what he had experienced. As long as he avoided the subject he was fine, but the moment he summoned up memories, he triggered this physiological response. The symptoms were transient. In the weeks that followed they faded away.

More striking is another of Porter’s experiences. While he retains strong memories of what he witnessed, he cannot recall any sounds from his time at the bomb-site. No wailing sirens, no shouts of the first responders, no cries from the victims. His memories are blanketed in a deep silence. Similarly, he cannot remember any smells linked to the blast. McVeigh had manufactured his 13-barrel bomb from ammonium nitrate, nitromethane, fertilizer and diesel fluid, all of which have a pungent odor that would have permeated the smoke at the site. Porter has no memory of this either. To him, this absence of sound and smell blunts some of the drama that was unfolding before him. This cleaving of two senses that are so intimately linked to traumatic events suggests the presence of dissociation, a separation of normally integrated mental processes. It occurs when the psyche is overwhelmed by the magnitude of an experience. In Porter’s case, it has left its stamp. Reflecting on those events 20 years back, he recalls a silent world, “like watching a movie on mute.” It doesn’t distress him. Just another leftover quirk from a day like no other.

Listening to Porter tell his story, I was struck by how different his life is from those photographers whose careers are defined by war and conflict. Absent is that relentless drive to return to the fray, to bear witness to suffering and to brave many dangers in doing so. From time to time, he picks up his camera for a wedding or sporting event. No more than that. He enjoyed his moment of fame. It never gave him a taste for more.

And yet Louis Pasteur was surely right when he observed that chance favours the prepared mind. Porter could not have foretold the Oklahoma bombing, but he kept his camera loaded and close. “Would you like to see my Pulitzer?” he asked as we made our way to the front door, the interview over. He stopped by a glass cabinet and opened it. Shifting aside the family china, he showed me his coveted prize.