He screamed as the bear – female grizzlies can weigh up to 25 stone in the US – stood on his back, biting and clawing his shoulder.
“She bit one of my legs, picking me up and slamming me on the ground multiple times,” Mr Burke said.
“She bit each leg from my buttocks to my inner knee about three times each. The final time I screamed again.
“This, unfortunately – but fortunately – turned her attention to my head.
“I believe she went in for a kill bite on my neck. I still had my hands interlocked and my arms protecting my carotid arteries.”
When the bear attempted to latch onto his neck it inadvertently bit into the canister, which exploded in its mouth and caused it to flee.
Bear repellent canisters often hold capsaicin, an irritant to the eyes and lungs, which can be sprayed in the event of an attack.
Mr Burke, who has been “shot at, mortared and [encountered] IED explosions”, later described the attack as “the most violent thing I have ever experienced”.