A man carrying a pistol and McDonald’s Happy Meal box attempted to rob a coffee shop in Milton Keynes on Saturday.
At around 6pm, the man walked to the counter of Starbucks in Elder Gate and shouted at the assistant to put money inside the McDonald’s box.
But the assistant refused to hand over any cash and the man left the coffee shop empty-handed.
Police have increased patrols in the area and are now offering extra safety advice to local businesses.
Investigating officer Det Con Wayne Watson said: “This was a serious offence and detectives are working to establish the circumstances.
“We would like to speak to the man in the CCTV as we believe he may have information related to this investigation.
“There were two customers in the shop at the time of the incident and we would like to speak to these people as they may have information which can assist officers.”
If you have any information about the incident please contact Det Con Watson via the 24-hour Thames Valley Police enquiry centre on 101.
If you don’t want to speak directly to the police, you can contact Crimestoppers anonymously on 0800 555 111.
No personal details are taken, information is not traced or recorded and you will not go to court.