An 18-year-old man suffered a fractured skull after he was struck on the head from behind in the early hours of Saturday, April 2.
The victim then saw a second man being struck in the head.
“This victim is currently unknown to the police and we would ask them to come forward,” a spokesman for Lancashire Police said.
Detectives on Tuesday (April 12) released an image of a man they wanted to speak to as part of their investigation.
Christopher Hodgkinson, aka Chris Johnston, is described as white, 5ft 8ins tall, with short brown hair.
His last known address was New Village in Ingleton, Carnforth.
Anyone who knows where he is should contact the police by calling 101 or emailing [email protected], quoting log number 0544 of April 3.
Independent charity Crimestoppers can also be contacted anonymously on 0800 555 111 or online at https://crimestoppers-uk.org/.