A man has been stabbed in the neck after asking a group of teenagers to stop throwing snowballs.
South Yorkshire Police said the 19-year-old victim challenged a group of youths for throwing snowballs "aggressively" at people in the street and at passing cars.
The attack took place between 8pm and 8.15pm on Thursday December 2 near a food shop in the Upperthorpe area of Sheffield.
The injured man required surgery on his wound and was later allowed home.
A police spokesman said: "A 19-year-old man was kicked, punched and stabbed in the neck with a sharp object, possibly a broken bottle, by a group of teenagers, after he attempted to stop them throwing snowballs aggressively at people in the street and passing cars.
"The group also assaulted his 19-year-old friend, who sustained a cut to his forehead and bruising to his face."
Police said the second victim required stitches to his forehead and was allowed home the same day.
The group, of about 15 males, are described as Asian and mixed race, aged between 15 and 20.
Police are appealing to anyone with information about the incident or who may have witnessed the attack to contact officers.
Chief Inspector Andy Male, from South Yorkshire Police, said: "We appreciate that when there is a fall of snow people will play around and throw snowballs, but I would like them to think about the effect of their actions on others when they throw them randomly at people.
"The fact this group decided to assault a member of the public for challenging their behaviour is not acceptable, and we are investigating it fully.
"Officers from Ecclesfield CID and the local Safer Neighbourhood Team are dealing with this incident."