This week, his own loved ones are mourning the sudden loss of the emergency doctor and mental health advocate at 61.
Mulholland – known affectionately as 'Dr Tom' – was a warm, generous person who spent his time focused on the wellbeing of others, says his friend Sam Hazeldine.
Hazeldine says he was watching his daughters horseriding when he got the news about Tom's death from their mutual friend Brooke Howard-Smith.
Since then, he's spent a lot of time reflecting on what happened.
"There was just so much he was trying to fight off in a health system that is struggling."
Among his many missions, Dr Tom toured rural New Zealand in a retro ambulance, promoting mental and physical health.
"He literally became the ambulance at the top of the cliff. With that ambulance, he drove around the country trying to help people prevent illness, rather than treat it.
"All I can imagine… he cared so much it just got too much for him."
Hazeldine's message to anyone affected by Dr Tom's death is to figure out the person that they'd call themselves if they were really struggling.
"Have a plan before things get to this point. Just agree you're gonna call someone. And if you're that person who receives a call, you are lucky to be in that privileged position."
In a 2021 interview, Dr Tom told RNZ that as an emergency department doctor, he saw a lot of illness that was preventable and his mission was to keep people out of hospital.
"There's a tsunami of diabetes, mental health issues… I'm just trying to get out there and get amongst it and try and prevent people turning up."
Seeing the massive need for doctors in rural New Zealand, he felt a sense of responsibility to help, but also loved visiting remote places.
"You park your boat and you wander up and do a couple of weeks mahi … you help out.
"I could have gone and worked overseas years ago… but you can't shoot a kingfish, sit under a kauri tree and listen to a tūī., can you, if you're overseas. And that's what's most important to me."
Over the years, Dr Tom spoke to thousands of rural New Zealanders and developed the wellness app KYND to help farmers track their own health.
He told Jesse Mulligan that one of his missions was to get farmers - who are too often isolated and overworked - to take as much care of themselves as they do of stock and machinery.
"When you're on the farm you're always looking out the window and there's always something to fix… its just hard to get that mental break. Burnout is a big problem."
When it comes to health and wellbeing, attitudes and behaviours are the most important things to change, Dr Tom said.
"It's not your cholesterol or your blood pressure that's gonna kill you. It's your attitude towards it that will.
"The point is if you make time for your wellness now, you're gonna have plenty of time to make up for your illness later."
Dr Tom said he'd been through a lot of stress in his own life, including a divorce and the 1994 Indonesian tsunami which killed over 200 people.
As a lifelong surfer, he spoke of learning how to use his thoughts and breathing to control his emotions in the face of big waves.
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