As a result his left arm was amputated (twice) later that year. It was the hardest time of his life.
"I felt like they had ruined my life and it took me a long time to get past that. I was angry for a long time and that acted like a roadblock to my own healing."
He still has his struggles. His life is riddled by phantom pain.
McSweeney moved to the Bay of Plenty from Matamata about four years ago for a better climate to help with his phantom pain.
He tried various sports, like rowing and shooting, but settled on triathlon.
He recently won the gold medal in his class - Tri 4 - a category for amputees. He came second in a field of five.
"I was rapt. That was a pretty huge achievement for me. This is only my first year in triathlon so I am trying to learn as much as possible."
With the guidance of coach Murray O'Donnell, with the assistance of Avanti Plus Mount Maunganui, he has been on a steep learning curve.
Having to figure out the best way to swim with one arm resulted in him adopting a dolphin-like technique
There have been many moments where he wanted to give up but he didn't let himself go there.
He made it through with the help and support of family, close friends and the New Zealand Rugby Foundation.
"Life goes on. It has to. There's no point standing still and feeling sorry for yourself. It wasn't getting me anywhere."
McSweeney has applied that award-winning attitude to his role with Athletics NZ, where he works with their schools programme.
He has lost 15kg since he took up triathlon and he now trains four times a week in each of the disciplines. It is the highlight of his day.