Niagara Regional Police are looking for a man they believe to be involved in an assault in Welland.
Officers were called to 260 King St., in the area of Albert and State streets just before midnight on Wednesday.
When they arrived, they found a man in his 50s with life-threatening injuries. He was taken to hospital where he remains in critical condition.
Police are not specifying what kind of injuries the man was suffering from, only saying they were sustained in an assault.
They are asking for help in locating the suspect described as a white man, 30 to 40 years old with a slim build and short dark hair.
Police say he was reported to also be wearing a dark hoodie and walking a large Bullmastiff-type dog.
Anyone with surveillance footage of the area or dashcam footage is being asked to call police, or Crime Stoppers at 1-800-222-8477 if they wish to remain anonymous.