OTTAWA—Canadian authorities warned 9 several years ago that Gabriel Wortman—the gunman police say was accountable for 22 fatalities for the duration of a violent weekend rampage in April—owned firearms, disliked the police and harbored feelings of killing regulation-enforcement officers.

Officials with the Royal Canadian Mounted Law enforcement disclosed the information Thursday at a information meeting, at which time they acknowledged they may hardly ever pin down Wortman’s motive that led to the deadliest shooting spree in Canadian history. The spree, around around a…