The Royal Canadian Mounted Police said George Phillips, 51, of Jaffray, British Columbia, also is charged with careless storage of a firearm, the Canadian Broadcasting Corp. reported.
Phillips' first court appearance is scheduled for Nov. 9 in Cranbrook.
Under Canadian law, children under 12 cannot be charged with criminal acts, the CBC noted.
Royal Canadian Mounted Police Cpl. Chris Faulkner said the 10-year-old boy was showing his stepfather's shotgun to Michael Voth, 17, of Fernie, June 16 when it fired, striking Voth, who was pronounced dead at the scene.
"There's only losers in this situation," Faulkner said. "So now we have a 17-year-old that's dead, we have the immediate effect on his family, his friends and the residents in the area.
"It's a traumatic situation for the 10-year-old boy to know that his actions have killed somebody."
Faulkner pointed out gun owners are required to follow strict rules regarding possession and storage of firearms.
"In this situation here, we feel that the owner was negligent in how he did store the firearms, and here we are with a death on our hands," he said.