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Scott G Winterton, Deseret News
Dr. Mark Mahan becomes emotional at the South Jordan Health Centeron Friday, Sept. 9, 2016, as he talks about how he decided to change careers — from New York investment banker to neurosurgeon — because of 9/11.

SALT LAKE CITY — Mark Mahan loved those towers.

Twenty-five years old and fresh out of college, he felt a thrill every time he emerged from the subway and saw the impossibly slender buildings rising above him.

Mahan worked at Deutsche Bank at 130 Liberty St., right next to the World Trade Center.

Sometimes if the young investment banker had time for lunch, he would cross the street and go into the lobby and stare at the three stories of lightness above him.

On the occasional night that the bank would hold functions at the north tower's rooftop restaurant, Mahan would look out the narrow windows and watch the city move. On breezy days, the towers would sway with the wind.

"Most people know them from the outside,” he said. “They were tall; they were slender. But they were gorgeous on the inside … You walked in, and you were like, 'How can this building even stand?'"

To the former Eagle Scout from Tulsa, Oklahoma, the Twin Towers were a beloved symbol of his madcap life on Wall Street in the '90s — a time when money flowed so freely that the financial transactions Mahan handled often accrued more interest in one night than he earned in an entire year.

He loved those towers.

Then they fell.

Mahan was 40 blocks away that day, working in the bank's new office building, when he saw the news. A college buddy had been on Flight 11.

On his walk back to his apartment, Mahan passed by hundreds of people covered in thick dust from the towers, picking their way home.

In the 15 years since, America has held vigils and memorials. A new tower has gone up. A museum has been built. Osama bin Laden was killed. Chris Rock did a bit on "Saturday Night Live." A mattress store made a commercial.

The memory of that day seems no easier to process.

"I can't look back," Mahan said. "I don't know if it was too sad or too frightening or too what. It was too much. It was too much loss that single day."

* * *

With the world on edge and New York under attack, Mahan searched for something new, “something more meaningful."

“I wanted to make sure I was helping people," he said. "I didn’t think I was, in finance.”

So Mahan settled on a career that many told him was foolish or impossible: He became a doctor.

Mahan hit the books. He got into medical school at Columbia University and decided to specialize in neurosurgery. He trained in San Diego and Phoenix, and when he realized there were no complex nerve reconstruction specialists between California and Missouri, he moved to Utah. He wanted to help.

Even today, Mahan visibly brightens when asked about his work.

"You can he tell he loves what he's doing and really cares about it,” said Jana White, a Draper mother who met Mahan two years ago when her 8-year-old son, Cooper, rolled off an 80-foot cliff in an ATV accident.

"Usually surgeons have a terrible bedside manner," White said. "(Mahan) came to Primary Children's all over the weekend. He kept checking in on (Cooper). He was just amazing."

It was Mahan who performed the 10-hour surgery on Cooper that enabled the child to regain use of his left arm. It was Mahan who pulled nerves from Cooper's tiny chest and legs to reconnect his arm and his brain. It was Mahan who chose to do one extra nerve graft “because he’s Cooper" and because it would give the boy a better chance of regaining use of his arm, White said.

White knew that Mahan gave up on a lucrative career in finance to become a doctor.

But "I never understood what changed," she said. "Something really changed his view of things for him to go back to school."

As a doctor, Mahan found a new purpose and new talent. His healing hands have grafted nerves, removed tumors, coaxed limbs back to life. He has coached patients through the success of regaining function and comforted them through the loss of it. He has watched kids like Cooper go from being paralyzed in one arm to mountain biking in Moab.

"That's what's special about kids," Mahan said. "Kids do a better job. They sometimes can put the past behind them a little bit better."

* * *

Mahan has kept himself busy: busy teaching residents, busy leading a research team, busy working at both University Hospital and the South Jordan Health Center.

He takes the stairs everywhere he goes. He runs during his lunch break, just like he used to run from his apartment to 130 Liberty St. He turns off the radio and the TV every second week in September.

He does not think about 9/11.

Fifteen years later, he says, it doesn't seem any clearer: Why it happened, why he was spared, how to mourn, how to grieve, how to extract redemption out of the rubble.

Every time NPR plays another piece on Sept. 11, Mahan skips it. Every time he goes back to New York, he avoids Ground Zero. The date on the calendar is a hole, a redacted strip of history, a spot too raw to touch.

"Sometimes," Mahan said, "you just don't look back."

Now, "I don't ever wonder about a different career," he added. "I don't ever wonder about, 'Should I have done this or should I be doing that?' I know what I need to do. I feel like it gives me a little bit of liberty to be the best physician I can be, to be the best surgeon, to take our art and move it forward."

Mahan keeps just two mementos: a box of his old notepads with the 130 Liberty St. letterhead, and a small aerial photograph of the World Trade Center, with the Deutsche Bank building right next to it.

He keeps the cheap black-and-white picture in his office at the hospital.

Sometimes he will sit and look at it and allow himself to remember how much he loved those towers.

Twitter: DaphneChen_