RCMP say the senior was walking out of the store on Thursday afternoon when he dropped the keys to his vehicle.
Another man picked up the keys but wouldn't give them to the senior and then attacked him with a blade of some kind before taking off in another vehicle.
Police believe drugs may be a factor in the assault.
Mounties have charged Steven Morris Firingstoney, 31, of Maskwacis, Alta., with aggravated assault, robbery, possession of a weapon for a dangerous purpose and possession of stolen property.
Firingstoney is in custody and will be in court on Tuesday.
(CHED, CTV Edmonton)