Detectives in Sheffield are linking an attempted robbery at a petrol station with an armed robbery at a shop later the same evening.
Police were called at 8.05pm on Sunday 19 October to the petrol station at Crystal Peaks after a man walked into the store posing as a customer.
When the assistant opened the till the offender pushed the member of staff and attempted to grab money from it. He then left empty handed.
He is described as white, around 18 or 19-years-old, around 5ft 4ins tall, of big build, and wearing a grey tracksuit and blue padded body warmer.
A second incident at Beighton Convenience Store was reported to police at 9.05pm the same evening.
A man threatened the member of staff with a knife and demanded money which was handed over to the offender. The victim did not suffer any injuries.
The offender is decribed as white and wearing a grey long-sleeved top under a dark padded body warmer.
Anyone with information about the robberies is asked to call South Yorkshire Police on 101 or they can contact Crimestoppers anonymously on 0800 555111.