A CCTV video of a man running has been released as detectives investigate an assault in Preston.
The images come after a man was attacked by three other men in Church Street.
Police believe the 19-year-old victim from Preston was attacked with weapons, before he was knocked to the ground and kicked and punched.
The man suffered a serious head injury and was taken to Royal Preston Hospital for treatment.
One of the alleged attackers was detained at the scene by a member of the public and later arrested by police. Two other men made off from the scene.
Det Con Abid Majid of Lancashire Police, said: “Do you recognise the males in the CCTV? We’re keen to identify and speak to them as part of our investigation.
"If you have any information at all, please come forward if you haven’t already.
Call 01772 209803 or 101 quoting crime reference SA1818521 with information.
Alternatively independent charity Crimestoppers can be contacted anonymously on 0800 555111 or online at crimestoppers-uk.org
A 17-year-old boy from Preston was arrested on suspicion of wounding and later released under investigation.