Two teenage boys were racially abused and then punched in the face in Bletchley on Saturday night.
The incident took place at around 9pm on March 23 outside Tesco Express in Melrose Avenue.
At around 9pm the 15-year-olds were outside the store when they noticed a man looking at them from inside the shop.
As the man left the shop, he approached the two boys and start using racist language. He then punched them both in the face.
Another man then grabbed hold of the suspect and pulled him away.
One of the boys sustained a broken nose and received treatment at Milton Keynes General Hospital. The other boy sustained cuts and bruises.
The offender is described as a white man in his thirties, approximately 5ft 9ins to 5ft 10ins tall, medium build with short blonde hair. He was wearing a blue jumper.
PC Martin Connor said: “I am appealing for anyone who witnessed this incident or who has any information that could help with this investigation to come forward.
“I would particularly like to speak to the member of the public who intervened as I believe he will be able to provide vital information about this incident. He is a white man, approximately 5ft 8ins to 5ft 10ins tall and of a stocky build. He was wearing a baseball cap and shorts.”
If you have information call Thames Valley Police 101, quoting reference number 43190089133. Alternatively, you can contact Crimestoppers anonymously on 0800 555 111.