Math teacher Jim O’Connor had a reputation amongst his students for being uncompromising. But one day, they found out what he did in his downtime, and they would never look at him the same way again.

As 70-year-old Vietnam veteran-turned-teacher Jim O’Connor wrote yet another seemingly impossible algebra equation on the whiteboard, his students exchanged puzzled looks. They knew by now that he was a tough taskmaster. But after a day of setting grueling calculus challenges, little did they know where the uncompromising O’Connor headed after class.

In fact, O’Connor had built up a reputation amongst the students of St. Francis High School, on the outskirts of Los Angeles, as not exactly being the warm and fuzzy type. “It drives me crazy when people say that school should be fun,” he told CBS News. “I mean, it’s nice if it could be, but you can’t make school fun.”

Nonetheless, he was certainly respected by his class for his undeniable academic knowledge and no-nonsense approach. Yet O’Connor didn’t strike the boys he taught as having much of a soft side. “If you look at the clock, you’re on his bad list for the rest of class,” student Michael Tinglof told the Los Angeles Times.

Another senior, Pat McGoldrick, added that before new students get to know O’Connor, “everybody thinks he’s being really mean.” And, of course, a bit of respect and discipline goes a long way as a teacher. “You want to teach a class with 30 boys, you’ve got to be strict,” O’Connor explained.

For a number of years, then, his reputation as a disciplinarian was set in stone. That was, until one day McGoldrick and Tinglof decided to set up a student blood initiative to boost vital supplies at Children’s Hospital Los Angeles. And while visiting the medical center, they were in for a surprise.

For a start, everyone was excited to hear that they were from St. Francis High School, and the pupils were asked if they knew a very special guy – Jim O’Connor. “Isn’t he wonderful?” medical staff commented. McGoldrick wondered if they were talking about the same person. “What? It was disbelief, really,” he told CBS. “He was like a celebrity there.”

The reason for O’Connor’s quasi-iconic status gradually started to become clear. Firstly, McGoldrick noticed a plaque in the center listing the hospital’s best donors. And there in gold lettering was the name of the top donor – none other than their teacher, Jim O’Connor.

In fact, it transpired that their schoolteacher had been donating blood to the children’s hospital for almost three decades. And by the time that his students visited the hospital, O’Connor was their best donor by some margin – having given an incredible 72 gallons.

The veteran’s blood is especially valuable as it is O-negative, meaning that anyone can receive it. As often as he has been allowed, O’Connor has been donating both blood and platelets, helping everyone from cancer patients to newborn babies. And the latter are an important part of another aspect of O’Connor’s life that he’d kept hidden from his students.

For not only did O’Connor selflessly give his blood to those in need, but he also gave his time to help care for sick babies. For three days a week over the course of two decades, the tough war veteran had worked as a TLC volunteer, cradling and rocking them, soothing the most troubled of infants. And he appears to have a knack for it.

“They tend to calm for him,” said nurse Erin Schmidt. “They tend to relax with him, they fall asleep with him.” Another nurse, Jeri Fonacier, agreed. “No matter how sick they are, no matter how devastated, he’s just so caring. He brings such a warmth and peace,” she told The Los Angeles Times.

This gift was perhaps all the more surprising given that O’Connor had never wed and or had children of his own. Nonetheless, he seemingly had a natural talent for caring for babies who are in distress. “I just like them and relate to them somehow,” he told CBS.

Nurses have suggested that the comfort the babies get from O’Connor is due to his deep voice, which relaxes them. But he believes that the infants merely respond well to being held by another human being. Moreover, experts agree that such contact is essential for distressed babies.

However, O’Connor’s motivation goes deeper than merely providing a soothing presence. The teacher of 38 years simply can’t bear to see babies left on their own when their parents are unable to be with them. “I don’t want to see them alone. You can’t do that,” he said, appearing to fight back tears.

There are many reasons why the babies’ own relatives may be absent. For instance, they could be busy caring for other children, working to support the family or reside too far from the hospital to visit regularly. Sadly, some parents might even be suspected of abuse and therefore not allowed access.

Image: Children’s Hospital Los Angeles via NBC News

But those were the babies and children that O’Connor was drawn to most of all. “The kids who have nobody, those are the ones who obviously need volunteers a lot. They just want to be held by somebody,” O’Connor said in an interview with NBC.

However, his stern alter ego was one that he perhaps still wanted to maintain. “You’re not a tough guy at all,” said CBS interviewer Steve Hartman, evidently moved by the benevolence of the hard-boiled man in front of him. “I know, but don’t tell my students!” O’Connor laughed in response.

And those students were understandably rocked by the revelations about his softer side. “I’ve always respected him, but now it’s to a different degree where I try and emulate him,” McGoldrick said. “He’s the epitome of a man of service.”

After keeping his double life secret for 20 years, it’s evident that humble O’Connor isn’t in it for the glory. Since the truth was uncovered, he’s been happy to talk about his actions, saying that he hopes to motivate his students and others to do the same. “If there are more people wanting to donate blood, wanting to volunteer, then that’s great,” he told NBC.

And his newfound fame wasn’t going to stop the so-called “baby whisperer” from doing what he did best. “We see him and we say, ‘Oh Jim, oh thank God you’re here,’” nurse Rebecca Day told The Los Angeles Times. And with accolades like that, who would want to?