Police in Stroud are trying to trace a woman who came to the rescue of a teenage boy when he was assaulted last month.
The unprovoked assault happened in London Road, near to Waitrose supermarket, at about 2pm on Wednesday, 27 September.
The 17-year-old has suffered blurred vision as a result of the assault and is receiving specialist treatment for his injury.
The woman officers would like to speak to intervened directly after the assault and may have important information about the circumstances.
She is believed to have been walking on the pavement in the same direction as the victim, from Waitrose towards the town centre. She is understood to have said: "Go home sweetie, I'll take care of this."
The offender was on the same pavement but walking in the opposite direction.
The woman is described as being white, in her mid-70s, slim to medium build, about 5ft 2 inches tall with straight, white, shoulder length hair.
She was wearing a three-quarter length grey coat, black tights and shoes and was pulling a red or dark coloured shopping trolley.
If you recognise the description or have any information about this incident please call Gloucestershire Constabulary on 101 or email firstname.lastname@example.org quoting incident 494 of 27/10
A 29-year-old man has been arrested on suspicion of assault and has been released under investigation.