CALGARY -- Police are looking to speak with a man who may have witnessed a serious assault at the Sunnyside LRT station over the weekend.

An elderly man was hit and fell onto the concrete platform about 9 a.m. on Saturday. He sustained a head injury and remains in hospital.

Police later arrested Basil Sweezey, 36, and charged with one count of aggravated assault.

After reviewing CCTV footage, investigators believe another man was on the platform at the time and may have witnessed the assault.

Anyone with information is asked to call the non-emergency line at 403-266-1234, the Homicide Tip Line at 403-428-8877 or Crime Stoppers at 1-800-222-8477.