Officials have described a fire that, in their account, started with a grenade launcher on the grenade range and then spread across a kilometre within seconds inside a zone crews were not able to enter.
A fifth Canadian soldier died from injuries he suffered when a grass fire swept through a military training area last month.
An investigation found that the fire was likely sparked by a grenade launcher being fired on the base's grenade range, officials said.
Military officials said at the time that the fire spread across a kilometre in a matter of seconds.
That pace took many of those on the base by surprise, the officials said.
Firefighters on the base had known about the fire but could not tackle it, officials said.
The fire was in a danger area that could contain unspent explosives, and that risk kept firefighters from moving in to fight the flames.
The sequence officials have set out runs from firing on the grenade range, to a grass fire that spread a kilometre in seconds, to injuries that have now proved fatal for a fifth soldier.