Born in Queensland, Australia, Gunner's family was made up of a mix of paramedics, firefighters, and law enforcement officers. Australia had started experimenting with RobCo International's "fire brigadier" Protectron model as a means of combating the deadly annual bushfires, but the robots were slow to deploy and unable to keep pace with the fire itself; by the time Gunner graduated from university, fire and rescue was one of the few emergency services that was still predominantly human-led. Having initially volunteered with the rural fire service whilst working in the social care sector, Gunner eventually transitioned to professional firefighting full-time. He spent several summers in the US, assisting with the wildfire effort in California, and eventually met his future husband, Joseph, in Los Angeles.
They dated long-distance for several years, although the plan was always to settle down on the west coast. The following year, Gunner lost his leg in the Lone Pine Wildfire. Joseph supported him throughout his recovery, but towards the end of Gunner's hospital stay he received the news that his infant nephew, Shaun, had been unexpectedly orphaned back in his native New Jersey. After several emotional discussions, Joseph and Gunner got married at Gunner's bedside - thereby securing him temporary residency - and moved to Boston, Massachusetts to be near Joseph's remaining family. Unfortunately, the adoption was never finalized. When Shaun was a year and a half old, nuclear war broke out across America. Gunner, Joseph and Shaun took refuge in a nearby Vault, unaware of the fact that it was actually an elaborate, government-sanctioned science experiment. When Gunner awoke from cryo-sleep in 2227, he discovered his husband dead in an adjoining pod, and their adoptive son nowhere to be found.
Gunner tries to see the best in people, and that's not even the thing that's going to get him killed. Affable and even-tempered, he's the living embodiment of a "gentle giant"; a big dude with a way of putting people at ease, and a manner that suggests he always knows exactly what he's doing. Even before the war, his fellow firefighters called him the man with the plan. In reality, Gunner was cast adrift when he woke up in hospital without his leg. Joseph and Shaun were anchors when he desperately needed them, but as he scours the wasteland for signs of his adopted son, Gunner can no longer tell if he's treading water, or just straight-up drowning.