Gary was born in Winnipeg, Manitoba on September 2, 1945 to Michael and Frances (nee Witowski) Mandziuk. Growing up in Winnipeg and Yorkton, Saskatchewan, he was the oldest of three siblings, raised alongside his brother Michael and sister Debra.

Following high school, he leveraged his baritone voice and launched his broadcasting career as a radio disc jockey before choosing to further his education. He continued working in radio both during his time at the University of Winnipeg and after his graduation, taking positions at various stations across Saskatchewan, Manitoba, and Ontario. Eventually, he transitioned from broadcasting into sales, joining the 3M company in Winnipeg as a Sales Representative. In 1979, Gary, along with his young family, relocated to Toronto where he served as a Regional Manager for 3M Healthcare. His career continued to grow through subsequent transfers to London, Ontario, and back to Toronto. A dedicated and loyal 3Mer, he served the company for over 40 years until his official retirement in 2009.

During retirement, leisure travel became a priority, which he shared with Marilyn as they visited numerous countries across Europe, Asia, and the Caribbean. He also enjoyed everything about being a grandparent, creating special experiences and spoiling them with sugary treats. As a devoted fan until the very end, he rarely missed a Blue Jays game.

Gary is survived by his wife, Marilyn; sister Debra and brother Michael (Beverley); his two daughters Alexis Dawson (Matt) in Toronto, and Kristina McCarter (Michael) in Boston; stepdaughters Beth Revelle (Joe) and Brenda Heatley; and grandchildren Micah and Aria Dawson, Lennox McCarter, Sophie and Gavin Revelle; many nieces, nephews and friends.

In lieu of flowers, please consider a donation to the Canadian Cancer Society. A link may be found under the donation tab at the top of this page.

A Memorial will be held at Mount Pleasant Funeral Centre (375 Mount Pleasant Rd., Toronto, ON), on Saturday, August 29, 2026 at 2pm, with time to gather one hour prior.

A link to livestream the service will be found at the top of this page at approximately 1:45 pm.