Officers were called to a home in the area of Eramosa Road and Callander Drive just before 9 p.m. on Sunday and found the couple suffering from the effects of the spray.
Officers also noted a strong odour of pepper spray in the area, police said. The man was taken to the hospital as a precaution.
“The homeowner advised he answered a knock at the door and found a male in a Halloween mask, who sprayed the resident and his wife before fleeing on foot,” police said.
Police said officers searched the area but did not locate the suspect.
“Police reviewed surveillance camera footage, which showed the suspect walking past the house then doubling back and knocking on the door,” the service said in a news release.
On Tuesday, police released an image from the surveillance video that shows the suspect wearing a black hoodie, black pants, black shoes and a white mask. The person was also carrying a white bag.
Police have described the mask as a Guy Fawkes mask.
Anyone with information is asked to call police at 519-824-1212 ext. 7164. Anonymous tips can be left with Crime Stoppers at 1-800-222-8477.