Waterloo Regional Police are hoping that anyone who may have witnessed an altercation at the Stanley Park Mall on Saturday will come forward.
Police say that two men met at the mall at around 2:30 p.m. to complete a deal they had reached on a classified website.
An altercation broke out and one man was left with serious injuries after being assaulted.
The other man fled the area in light coloured pick-up truck.
The suspect is being described as a white male, in his 40s with a stocky build.
Police are asking anyone with information to call 519-570-9777 ext. 4499 or Crime Stoppers at 1-800-222-8477.